Refactor feature flags to use functional availability rules

[SamMorrowDrums]

Summary

• replace FeatureFlagEnable, FeatureFlagEnableAll, and FeatureFlagDisable with typed functional FeatureRule predicates
• add public inventory.FeatureFlag and FeatureResolver types for local and remote server consumers
• deduplicate declared feature checks into request-owned state shared by inventory filtering and ToolDependencies.IsFeatureEnabled
• keep handler-only checks lazy and fail closed while caching each resolved flag
• preserve the separate user-controllable AllowedFeatureFlags/header allowlist
• migrate granular, consolidated, MCP Apps, issue dependency, duplicate detection, and file blame gates
• document the new contributor workflow

Breaking change

Inventory items now expose FeatureRule instead of the three legacy feature-gate fields, and FeatureFlagChecker accepts inventory.FeatureFlag instead of string.

Validation

• script/lint
• script/test
• script/generate-docs

[Copilot]

Pull request overview

Refactors feature gating around typed functional rules and shared request-scoped resolution.

Changes:

• Introduces FeatureFlag, FeatureRule, and cached resolution state.
• Migrates inventory items and GitHub tools from legacy flag fields.
• Updates HTTP/stdio integration, tests, generators, and documentation.

Show a summary per file

File	Description
script/print-mcp-diff-configs/main.go	Uses the header-compatible flag accessor.
pkg/inventory/server_tool.go	Replaces legacy tool gates with FeatureRule.
pkg/inventory/resources.go	Adds resource feature rules.
pkg/inventory/registry.go	Collects and pre-resolves required features.
pkg/inventory/registry_test.go	Migrates inventory feature tests.
pkg/inventory/prompts.go	Adds prompt feature rules.
pkg/inventory/filters.go	Evaluates functional rules during filtering.
pkg/inventory/features.go	Implements typed rules and resolution state.
pkg/inventory/features_test.go	Tests predicates and caching.
pkg/inventory/builder.go	Removes the legacy feature filter.
pkg/http/server.go	Adapts HTTP feature resolution to typed flags.
pkg/http/server_test.go	Updates HTTP checker tests.
pkg/http/handler.go	Seeds request-owned feature state.
pkg/http/handler_test.go	Migrates handler feature tests.
pkg/github/ui_tools.go	Migrates the UI tool gate.
pkg/github/ui_tools_test.go	Verifies the UI feature rule.
pkg/github/ui_capability_test.go	Uses typed UI flags.
pkg/github/tools.go	Types granular flags and converts header flags.
pkg/github/tools_validation_test.go	Updates gated-duplicate validation.
pkg/github/server.go	Updates feature configuration documentation.
pkg/github/server_test.go	Updates dependency stubs.
pkg/github/repositories.go	Migrates file-blame gating.
pkg/github/repositories_test.go	Verifies file-blame rules.
pkg/github/pullrequests.go	Migrates consolidated PR rules.
pkg/github/pullrequests_granular.go	Migrates granular PR rules.
pkg/github/issues.go	Migrates consolidated issue rules.
pkg/github/issues_test.go	Updates issue-rule assertions.
pkg/github/issues_granular.go	Migrates granular issue rules.
pkg/github/issue_dependencies.go	Migrates dependency-tool gates.
pkg/github/issue_dependencies_test.go	Updates dependency gate tests.
pkg/github/granular_tools_test.go	Tests granular functional rules.
pkg/github/find_duplicate.go	Migrates duplicate-detection gating.
pkg/github/find_duplicate_test.go	Updates duplicate gate tests.
pkg/github/feature_flags.go	Types flags and defines reusable rules.
pkg/github/feature_flags_test.go	Migrates feature-resolution tests.
pkg/github/dependencies.go	Shares resolution through dependencies.
pkg/github/dependencies_test.go	Updates dependency checker tests.
pkg/github/csv_output_test.go	Migrates CSV rule fixtures.
pkg/github/context_tools_test.go	Uses typed IFC flags.
pkg/github/actions_test.go	Updates functional-rule terminology.
internal/ghmcp/server.go	Adapts stdio feature checking.
docs/insiders-features.md	Documents shared functional resolution.
docs/feature-flags.md	Documents availability rules.
cmd/github-mcp-server/generate_docs.go	Updates default documentation checker.
cmd/github-mcp-server/feature_flag_docs.go	Types feature documentation generation.

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• Files reviewed: 45/45 changed files
• Comments generated: 4
• Review effort level: Balanced