Centralize file conventions across discovery, watch, and bundling

[bcomnes]

Summary

Closes #296. Stacked on #303.

• Centralize filenames, suffixes, runtime-dependent TypeScript support, draft names, and bundle/rebuild categories in a small internal convention registry.
• Reuse the definitions in discovery, watcher filtering/classification, esbuild entry selection, and static-copy exclusions.
• Preserve the existing discovery exports and filename precedence.
• Fix the mismatch where JSX/TSX clients were supported by discovery and esbuild but excluded from watch add/remove events.

Validation

• Full Node suite, TypeScript, ESLint, installed dependency checks, and Playwright passed after rebasing onto the merged layout/subscription work.
• Filesystem-watch tests used Chokidar polling because native watchers are exhausted on this host.
• All three convention tests and the 26-test watch suite pass, including JSX client add/remove, global-data-only imports, and failed-build recovery.

Merge order

Merge #303 before this PR. The watch-planner PR is based on this branch so its review diff only contains the planner extraction.

[coveralls]

Coverage Report for CI Build 34161114939

Coverage decreased (-0.04%) to 95.897%

Details

• Coverage decreased (-0.04%) from the base build.
• Patch coverage: 138 of 138 lines across 5 files are fully covered (100%).
• No coverage regressions found.

Uncovered Changes

No uncovered changes found.

Coverage Regressions

No coverage regressions found.

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Coverage Stats

Relevant Lines:	7951
Covered Lines:	7776
Line Coverage:	97.8%
Relevant Branches:	1945
Covered Branches:	1714
Branch Coverage:	88.12%
Branches in Coverage %:	Yes
Coverage Strength:	293.88 hits per line

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💛 - Coveralls