Generate TypeScript API types from the Rust schema

[melonamin]

What changed

• add a deterministic generator from docs/api_schema.json to committed packages/core/src/generated/api-types.ts
• retain packages/core/src/types.ts as the ergonomic browser/WASM layer for encoding, completion, splitting, exports, runtime constants, helpers, and narrow public refinements
• check generated declarations in schema compatibility and core TypeScript typecheck paths
• expand schema compatibility coverage to every Rust schema root/definition and the complete runtime dialect enum
• add a headless Chromium integration harness that loads the real built WASM, initializes it, and analyzes a representative join query
• document regeneration, checks, and the real-WASM test command

Why

The public TypeScript models were handwritten mirrors of Rust and could drift silently; the previous schema tests validated only three sample values and most package tests mocked WASM.

Validation

• just update-schema
• just check-schema
• yarn workspace @pondpilot/flowscope-core build
• yarn workspace @pondpilot/flowscope-core build:no-wasm
• yarn workspace @pondpilot/flowscope-core typecheck
• yarn workspace @pondpilot/flowscope-core lint
• yarn workspace @pondpilot/flowscope-core test --silent (46 tests)
• just test-wasm-browser
• yarn workspace @pondpilot/flowscope-react build
• yarn workspace @pondpilot/flowscope-react lint
• yarn workspace @pondpilot/flowscope-react test --silent (204 tests)
• yarn workspace @pondpilot/flowscope-app typecheck
• just fmt-check-ts
• codex review --uncommitted — clean after fixing both accepted findings