chat: add turn timing metadata

[justschen]

• Carries authoritative start and end timestamps through turn lifecycle actions so clients can render consistent timing information.
• Persists turn start times and derived durations in state while preserving compatibility with older completed turns.
• Keeps reducer behavior aligned across TypeScript, Rust, Kotlin, Swift, and Go, including invalid timestamp handling.
• Regenerates schemas and client wire types and extends shared conformance fixtures.

References microsoft/vscode#325061

(Commit message generated by Copilot)

[Copilot]

Pull request overview

Adds authoritative turn timing metadata to the chat turn lifecycle so all clients can display consistent “started at” and “duration” information, and reducers stop synthesizing timestamps locally for turn boundaries.

Changes:

• Extend chat turn lifecycle actions to carry startedAt / endedAt, and extend turn state to expose startedAt / duration.
• Update reducers (TypeScript, Rust, Kotlin, Swift, Go) to validate timestamps, propagate authoritative timestamps into modifiedAt, and compute/clamp turn duration.
• Regenerate schemas and client wire types, add cross-language reducer fixtures, and add a changelog fragment.

Show a summary per file

File	Description
types/channels-chat/actions.ts	Adds startedAt/endedAt to turn lifecycle actions.
types/channels-chat/state.ts	Exposes startedAt/duration on completed turns; requires startedAt on active turns.
types/channels-chat/reducer.ts	Validates timestamps, uses authoritative timestamps for modifiedAt, computes/clamps duration.
types/reducers.test.ts	Updates fixture-driven test inputs for required startedAt.
types/test-cases/reducers/005-session-turnstarted.json	Updates fixtures for required startedAt and modifiedAt behavior.
types/test-cases/reducers/006-turnstarted-with-queuedmessageid-removes-from-queuedmessages.json	Updates fixtures for required startedAt and modifiedAt behavior.
types/test-cases/reducers/007-turnstarted-with-queuedmessageid-removes-last-queued-message.json	Updates fixtures for required startedAt and modifiedAt behavior.
types/test-cases/reducers/008-turnstarted-with-queuedmessageid-removes-matching-steering-message.json	Updates fixtures for required startedAt and modifiedAt behavior.
types/test-cases/reducers/009-turnstarted-without-queuedmessageid-does-not-touch-pending-messages.json	Updates fixtures for required startedAt and modifiedAt behavior.
types/test-cases/reducers/010-session-delta-appends-content.json	Updates fixtures for required startedAt on activeTurn.
types/test-cases/reducers/011-session-delta-with-wrong-turnid-is-no-op.json	Updates fixtures for required startedAt on activeTurn.
types/test-cases/reducers/013-session-responsepart-adds-to-responseparts.json	Updates fixtures for required startedAt on activeTurn.
types/test-cases/reducers/014-session-turncomplete-finalizes-turn.json	Updates fixtures for endedAt and expected duration.
types/test-cases/reducers/015-session-turncancelled-finalizes-turn.json	Updates fixtures for endedAt and expected duration.
types/test-cases/reducers/016-session-error-finalizes-turn-with-error.json	Updates fixtures for endedAt and expected duration.
types/test-cases/reducers/017-turncomplete-force-cancels-in-progress-tool-calls.json	Updates fixtures for endedAt and expected duration.
types/test-cases/reducers/018-turncomplete-with-wrong-turnid-is-no-op.json	Updates fixtures for endedAt presence on the action.
types/test-cases/reducers/019-tool-call-full-lifecycle-start-delta-ready-confirmed-complete.json	Updates fixtures for required startedAt on activeTurn.
types/test-cases/reducers/020-tool-call-ready-with-auto-confirm-transitions-to-running.json	Updates fixtures for required startedAt on activeTurn.
types/test-cases/reducers/021-tool-call-denied-transitions-to-cancelled.json	Updates fixtures for required startedAt on activeTurn.
types/test-cases/reducers/022-tool-call-result-confirmation-pending-approved.json	Updates fixtures for required startedAt on activeTurn.
types/test-cases/reducers/023-tool-call-result-denied-cancelled-with-result-denied-reason.json	Updates fixtures for required startedAt on activeTurn.
types/test-cases/reducers/024-tool-call-complete-from-pending-confirmation-defaults-confirmed.json	Updates fixtures for required startedAt on activeTurn.
types/test-cases/reducers/025-tool-call-actions-for-unknown-toolcallid-are-no-op.json	Updates fixtures for required startedAt on activeTurn.
types/test-cases/reducers/026-toolcallready-transitions-running-tool-back-to-pending-confirmation.json	Updates fixtures for required startedAt on activeTurn.
types/test-cases/reducers/027-toolcallready-re-confirmation-approved-transitions-back-to-running.json	Updates fixtures for required startedAt on activeTurn.
types/test-cases/reducers/028-toolcallready-re-confirmation-denied-transitions-to-cancelled.json	Updates fixtures for required startedAt on activeTurn.
types/test-cases/reducers/029-toolcallready-ignores-non-streaming-non-running-tool-calls.json	Updates fixtures for required startedAt on activeTurn.
types/test-cases/reducers/031-session-usage-updates-usage-on-active-turn.json	Updates fixtures for required startedAt on activeTurn.
types/test-cases/reducers/032-session-reasoning-appends-reasoning-content.json	Updates fixtures for required startedAt on activeTurn.
types/test-cases/reducers/067-session-truncated-drops-active-turn.json	Updates fixtures for required startedAt on activeTurn.
types/test-cases/reducers/068-session-truncated-drops-active-turn-even-when-clearing-all.json	Updates fixtures for required startedAt on activeTurn.
types/test-cases/reducers/070-full-turn-flow-with-tool-calls-and-re-confirmation.json	Updates fixtures for endedAt and expected duration.
types/test-cases/reducers/075-turnstarted-clears-isread.json	Updates fixtures for startedAt and modifiedAt behavior.
types/test-cases/reducers/084-toolcall-contentchanged-updates-running.json	Updates fixtures for required startedAt on activeTurn.
types/test-cases/reducers/085-toolcall-contentchanged-noop-non-running.json	Updates fixtures for required startedAt on activeTurn.
types/test-cases/reducers/086-toolcall-contentchanged-replaces-existing.json	Updates fixtures for required startedAt on activeTurn.
types/test-cases/reducers/090-toolcalldelta-wrong-turnid-is-no-op.json	Updates fixtures for required startedAt on activeTurn.
types/test-cases/reducers/091-responsepart-wrong-turnid-is-no-op.json	Updates fixtures for required startedAt on activeTurn.
types/test-cases/reducers/092-toolcallstart-wrong-turnid-is-no-op.json	Updates fixtures for required startedAt on activeTurn.
types/test-cases/reducers/093-usage-wrong-turnid-is-no-op.json	Updates fixtures for required startedAt on activeTurn.
types/test-cases/reducers/094-delta-nonexistent-partid-is-no-op.json	Updates fixtures for required startedAt on activeTurn.
types/test-cases/reducers/095-toolcalldelta-wrong-status-is-no-op.json	Updates fixtures for required startedAt on activeTurn.
types/test-cases/reducers/096-toolcallconfirmed-wrong-status-is-no-op.json	Updates fixtures for required startedAt on activeTurn.
types/test-cases/reducers/097-toolcallcomplete-wrong-status-is-no-op.json	Updates fixtures for required startedAt on activeTurn.
types/test-cases/reducers/098-toolcallresultconfirmed-wrong-status-is-no-op.json	Updates fixtures for required startedAt on activeTurn.
types/test-cases/reducers/099-endturn-force-cancels-running-tool-call.json	Updates fixtures for endedAt and expected duration.
types/test-cases/reducers/100-delta-targeting-toolcall-partid-is-no-op.json	Updates fixtures for required startedAt on activeTurn.
types/test-cases/reducers/101-toolcalldelta-without-invocationmessage.json	Updates fixtures for required startedAt on activeTurn.
types/test-cases/reducers/102-reasoning-targeting-non-reasoning-is-no-op.json	Updates fixtures for required startedAt on activeTurn.
types/test-cases/reducers/103-delta-skips-parts-without-id.json	Updates fixtures for required startedAt on activeTurn.
types/test-cases/reducers/105-session-input-full-draft-and-complete-flow.json	Updates fixtures for required startedAt on activeTurn.
types/test-cases/reducers/106-session-input-requested-with-drafts-status.json	Updates fixtures for required startedAt on activeTurn.
types/test-cases/reducers/107-session-input-turn-end-cleans-turn-scoped-only.json	Updates fixtures for endedAt and expected duration.
types/test-cases/reducers/108-session-input-upsert-and-clear-answer.json	Updates fixtures for required startedAt on activeTurn.
types/test-cases/reducers/110-session-input-completion-and-truncation-filtering.json	Updates fixtures for required startedAt on activeTurn.
types/test-cases/reducers/111-toolcall-pending-confirmation-sets-input-needed-status.json	Updates fixtures for required startedAt on activeTurn.
types/test-cases/reducers/112-toolcall-pending-result-confirmation-sets-input-needed-status.json	Updates fixtures for required startedAt on activeTurn.
types/test-cases/reducers/127-toolcallready-with-confirmation-options.json	Updates fixtures for required startedAt on activeTurn.
types/test-cases/reducers/128-toolcallconfirmed-approved-with-selectedoption.json	Updates fixtures for required startedAt on activeTurn.
types/test-cases/reducers/129-toolcallconfirmed-denied-with-selectedoption.json	Updates fixtures for required startedAt on activeTurn.
types/test-cases/reducers/130-selectedoption-carries-through-to-completed.json	Updates fixtures for required startedAt on activeTurn.
types/test-cases/reducers/131-selectedoption-carries-through-result-confirmation.json	Updates fixtures for required startedAt on activeTurn.
types/test-cases/reducers/132-selectedoption-carries-through-result-denied.json	Updates fixtures for required startedAt on activeTurn.
types/test-cases/reducers/158-toolcallconfirmed-approved-with-editedtoolinput-overrides-original.json	Updates fixtures for required startedAt on activeTurn.
types/test-cases/reducers/161-chat-turn-lifecycle-on-chat.json	Updates lifecycle fixtures for startedAt/endedAt and duration.
types/test-cases/reducers/163-toolcallstart-carries-mcp-contributor-through-lifecycle.json	Updates fixtures for required startedAt on activeTurn.
types/test-cases/reducers/220-toolcall-actions-update-meta.json	Updates fixtures for required startedAt on activeTurn.
types/test-cases/reducers/235-session-input-completion-records-declined-request-in-turn.json	Updates fixtures for required startedAt on activeTurn.
types/test-cases/reducers/237-session-input-completion-no-op-unknown-id-with-open-requests.json	Updates fixtures for required startedAt on activeTurn.
types/test-cases/reducers/238-invalid-turn-start-timestamp-is-no-op.json	Adds fixture coverage for invalid startedAt no-op behavior.
types/test-cases/reducers/239-invalid-turn-end-timestamp-is-no-op.json	Adds fixture coverage for invalid endedAt no-op behavior.
types/test-cases/reducers/240-turn-duration-is-clamped-to-zero.json	Adds fixture coverage for negative duration clamping.
schema/actions.schema.json	Regenerates action schema with startedAt/endedAt requiredness.
schema/commands.schema.json	Regenerates command schema to reflect updated action/state shapes.
schema/errors.schema.json	Regenerates error schema to reflect updated action/state shapes.
schema/notifications.schema.json	Regenerates notification schema to reflect updated state shapes.
schema/state.schema.json	Regenerates state schema with startedAt/duration and ActiveTurn.startedAt required.
docs/.changes/20260709-turn-timing.json	Adds changelog fragment documenting the user-visible protocol change.
clients/swift/AgentHostProtocol/Sources/AgentHostProtocol/Reducers.swift	Updates Swift reducer to validate and propagate timestamps and compute duration.
clients/swift/AgentHostProtocol/Sources/AgentHostProtocol/Generated/Actions.generated.swift	Regenerates Swift action wire types for new fields.
clients/swift/AgentHostProtocol/Sources/AgentHostProtocol/Generated/State.generated.swift	Regenerates Swift state wire types for new fields.
clients/swift/AgentHostProtocol/Tests/AgentHostProtocolTests/ReducersTests.swift	Updates Swift reducer tests for required timestamps and modifiedAt semantics.
clients/swift/AgentHostProtocol/Tests/AgentHostProtocolTests/NativeReducerTests.swift	Updates Swift native reducer test state setup for required startedAt.
clients/kotlin/src/main/kotlin/com/microsoft/agenthostprotocol/Reducers.kt	Updates Kotlin reducer to validate timestamps and compute duration/modifiedAt from action timestamps.
clients/kotlin/src/main/kotlin/com/microsoft/agenthostprotocol/generated/Actions.generated.kt	Regenerates Kotlin action wire types for new fields.
clients/kotlin/src/main/kotlin/com/microsoft/agenthostprotocol/generated/State.generated.kt	Regenerates Kotlin state wire types for new fields.
clients/kotlin/src/test/kotlin/com/microsoft/agenthostprotocol/ReducersTest.kt	Updates Kotlin reducer tests to assert timestamp propagation.
clients/rust/crates/ahp/src/reducers.rs	Updates Rust reducer to validate timestamps, propagate modifiedAt, and compute duration.
clients/rust/crates/ahp-types/src/actions.rs	Regenerates Rust action wire types for new fields.
clients/rust/crates/ahp-types/src/state.rs	Regenerates Rust state wire types for new fields.
clients/rust/crates/ahp/Cargo.toml	Adds chrono dependency used for RFC3339 parsing in reducer.
clients/rust/Cargo.toml	Adds/pins chrono in the Rust workspace.
clients/rust/Cargo.lock	Updates lockfile for chrono and transitive deps.
clients/go/ahp/reducers.go	Updates Go reducer to validate timestamps, propagate modifiedAt, and compute duration.
clients/go/ahptypes/actions.generated.go	Regenerates Go action wire types for new fields.
clients/go/ahptypes/state.generated.go	Regenerates Go state wire types for new fields.
clients/go/examples/reducers_demo/main.go	Updates Go example usage for required timestamps.

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