feat(enrichment): Native-build / install-cost dependency flag

[JSONbored]

Context

A REES (review-enrichment service) analyzer. Tier: solid.

Detects: A newly added dep that triggers a native compile on install (node-gyp, no prebuilt binary) or has no pure-Python wheel — hidden CI cold-start/install cost and a frequent cross-platform breakage source.

Data source: npm registry JSON scripts/gypfile/binary fields + deps.dev; PyPI JSON urls to check sdist-only (no bdist_wheel). Free, keyed on package@version from the shipped extractor.

This is heavy/external/historical analysis the no-checkout headless claude --print reviewer cannot do; the REES returns it as a brief block the engine splices into the review (additive + fail-safe).

Implementation (established pattern, all inside review-enrichment/)

1. Finding type + BriefFindings key in src/types.ts
2. src/analyzers/<name>.ts — pure, inject fetch for tests
3. Register in src/brief.ts ANALYZERS registry
4. Render a public-safe block in src/render.ts
5. node:test units against dist/ + a live smoke against the real data source

Deliverables

• The analyzer + wiring + tests + a verifiable brief block (file:line or package@version)
• Clean PR off main (zero engine conflict; outside the engine tsc/vitest/codecov scope)

Parent: #1499