fix(build): clean stale output and streamline verification

[yyyyaaa]

Summary

• stop ignoring obsolete apps/blocks/.source output so stale generated files cannot remain hidden
• align the runtime contract with the GitHub Actions that are actually used
• keep pnpm check focused on contracts, generated docs, fixtures, typechecking, and tests
• preserve Storybook, registry install, and package artifact verification under pnpm check:full
• remove 65 repetitive leaf-component test files while retaining compiler, package, docs-generation, API, accessibility, runtime, and representative complex-flow coverage

Test audit

• total tests: 1,209 → 439
• Blocks tests: 1,113 across 96 files → 343 across 31 files
• pnpm check: 57.41s → 38.91s

Verification

• pnpm check
• pnpm build
• pnpm build:pages
• pnpm pack:local
• exercised representative docs routes locally; all returned 200 and .source was not regenerated