perf(lint): load Sucrase lazily in validateReactPages

[os-zhuang]

Summary

@objectstack/lint sits on the kernel boot path, but the react syntax gate (ADR-0081) only runs when a kind:'react' page is actually validated. The top-level import { transform } from 'sucrase' in validate-react-pages.ts made every boot parse ~1.5 MB of transpiler (~16 ms cold require) — the same boot-path problem as the TypeScript compiler in validateReactPageProps, fixed in #2544.

• Sucrase now loads on the first validated react-source page via the same deferred createRequire pattern (anchor chain import.meta.url → __filename → cwd); the public API stays synchronous and unchanged, and sucrase stays a regular dependency in package.json.
• If the package is missing at call time (image pruning), validation fails with an actionable error instead of killing boot. The loader call sits outside the transpile try so a missing package can't be swallowed as a syntax finding.
• The boot-path guard test is generalized from lazy-typescript.test.ts to lazy-deps.test.ts, parameterized over LAZY_DEPS = ['typescript', 'sucrase'] at all three levels: structural no-eager-import scan over src, child-process probes of both built dist formats (also asserting per-gate independence — the syntax gate must not load typescript), and in-process lazy-load behavior. An in-worker require.cache probe alone cannot catch a reintroduced eager import: vitest inlines static imports through its transform.

Red-check

Verified the guard goes red for each dep separately by reintroducing the eager imports (string-patched, then reverted):

• both deps eager → all 4 guard tests fail; the structural scan names both offenders
• sucrase-only eager → dist probes fail specifically with sucrase was loaded eagerly, at import time

Verification

• pnpm vitest run in packages/lint: 116/116 green, all 4 guard tests run un-skipped against built dist
• eslint src clean
• turbo build --filter=...@objectstack/lint: 61/61 tasks green
• changeset: patch for @objectstack/lint

🤖 Generated with Claude Code

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Project	Deployment	Actions	Updated (UTC)
spec	Ready	Preview, Comment	Jul 3, 2026 2:13pm

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📓 Docs Drift Check

No hand-written docs reference the 1 changed package(s). ✅