feat(consumer): versioned IR manifest + drift-check (WHYNOT-WP-0003 T03-T07,T09)

Make ir/ the unit of versioned downstream consumption so consuming repos can
pin a version, inspect it, and follow changes at their own pace.

- T03 ir/manifest.json: per-version inventory + diff anchor with deterministic
  sha256-over-canonicalised-JSON hashes; no-churn generatedAt; manifest schema.
- T07 ir/INDEX.md: human-readable catalog generated by make ir.
- T04 .whynot-design.lock sync-point format + lock schema.
- T05 npx @whynot/design drift: consumer drift-check (bin entry), exit 0/2/3,
  --json/--update/--manifest/--version/--lock.
- T06 CONSUMING.md guide + examples/consumer-fixture/ runnable demo; README +
  MultiFrameworkSupport cross-links; fix README version pin (@0.3.0 not @v0.3.0).
- T09 CONSUMER_CONTRACT_PARITY.md design-only note (live-UI parity deferred).

T02 (publish) and T08 (showcase, blocked on WP-0002 T11) remain wait. Repo stays
in dev mode; no outward publish performed.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

MultiFrameworkSupport.md

@@ -23,6 +23,11 @@ That tag is valid in:
 
 You do not write a different component per framework. You write the same custom element. The framework decides how to pass props (`variant="primary"` in HTML, `variant="primary"` in JSX, `:variant="…"` in Vue).
 
+> **Tracking versions, not just using them.** Whatever framework you wire it into, a
+> consuming repo also pins a version and follows changes at its own pace via the
+> technology-neutral IR + the `npx @whynot/design drift` check. See
+> [`CONSUMING.md`](./CONSUMING.md).
+
 ---
 
 ## Architecture recap