Resolve #2890: improve the React typegen testing loop

[ayden94]

Summary

Add deterministic check and watch workflows for React page type generation, atomic versioned artifacts, and a canonical consumer testing recipe without introducing a source scanner or client route matcher.

Linked context: Closes #2890

Changes

• add non-mutating fluo typegen --check behavior with stable results and exit semantics
• add a bounded typegen watch lifecycle with coalescing, shutdown, failure recovery, and last-valid artifact preservation
• make generated artifacts versioned and atomic while retaining HandlerDescriptor/createReactPageCatalog(...) ownership
• expose stable CLI automation contracts and help output
• add request, hydration, generated-route, and JavaScript-disabled consumer testing guidance and fixtures without adding a React-specific testing helper
• synchronize CLI, React, Testing, toolchain, testing-guide, example, and context documentation in English and Korean
• add minor changesets for @fluojs/cli and @fluojs/react

Testing

• pnpm build && pnpm typecheck
• isolated pnpm verify:release-readiness
• focused Vitest: 7 files, 36 tests
• pnpm verify:public-export-tsdoc
• pnpm docs:sync-check
• pnpm verify:platform-consistency-governance
• pnpm verify:changeset-release-lane -- --lane=stable --base-ref=a7cffb16
• React example Playwright: 2 tests
• changed-file Biome, LSP diagnostics, and git diff --check

The optional no-excuse tool could not run because it requires typescript/unstable/* APIs unavailable in the repository's typescript@6.0.2; canonical build, typecheck, tests, docs, governance, public TSDoc, and release-readiness checks passed.

Release impact

• This PR has consumer-visible release impact and includes a changeset.
• This PR has no consumer-visible release impact.

Public export documentation

• Changed public exports include a source-level summary.
• Changed exported functions document matching @param / @returns tags where applicable.
• Source @example blocks and README scenario examples still play complementary roles.

Behavioral contract

• No documented behavioral contracts were removed without migration notes.
• New behavioral contracts are documented in the affected package README.
• Intentional limitations are explicitly stated (not silently removed).
• Runtime invariants are covered by regression tests.

Generation remains based on bootstrapped HTTP descriptors and the React page catalog. Check/watch workflows do not scan source routes or create a runtime matcher.

Platform consistency governance (SSOT)

• SSOT English/Korean mirror structure remains synchronized for changed governance docs.
• If platform contract docs changed, companion updates include discoverability/docs index, tooling or CI enforcement, and regression-test evidence.
• Any package README alignment/conformance claims are backed by the applicable platform harness tests, such as createPlatformConformanceHarness(...) for platform component contracts or createHttpAdapterPortabilityHarness(...) for HTTP adapter portability contracts.

No platform adapter contract changes. EN/KO toolchain and testing contracts remain synchronized and are backed by focused process and browser tests.