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>

ir/SCHEMA.md

@@ -24,11 +24,50 @@ ir/
   schema/
     tokens.schema.json       ← JSON Schema for tokens.json (W3C DTCG)
     component.schema.json    ← JSON Schema for each components/<Name>.json
+    manifest.schema.json     ← JSON Schema for manifest.json (version + hashes)
   tokens.json                ← all design tokens, W3C DTCG format   (emitted by T05)
   components/<Name>.json      ← one contract per component           (emitted by T05)
   exemplars/<Name>.{png,html} ← reference render from the designbook (emitted by T05)
+  manifest.json              ← per-version inventory + diff anchor   (WHYNOT-WP-0003 T03)
+  INDEX.md                   ← human-readable catalog                (WHYNOT-WP-0003 T07)
 ```
 
+## Version manifest (`manifest.json`) — the diff anchor
+
+`ir/manifest.json` is the unit of **versioned consumption**. A consuming repo never
+reads the Lit internals; it pins a published `@whynot/design@X.Y.Z` and tracks the
+manifest. Shape:
+
+```json
+{
+  "schemaVersion": "1.0.0",
+  "designVersion": "0.3.0",
+  "generatedAt": "2026-06-27T17:28:08.913Z",
+  "tokensHash": "sha256:426f565a9ce6c36f",
+  "components": [
+    { "name": "Button", "group": "atoms", "hash": "sha256:4a32713049e433dd" }
+  ]
+}
+```
+
+- **Each `hash`** is `sha256:` + the first 16 hex chars of a sha256 over the
+  *canonicalised* contract (keys sorted recursively, no insignificant whitespace).
+  Canonicalisation makes the hash invariant to formatting and sensitive **only** to
+  meaningful change — re-running `make ir` after a no-op edit yields the same hash.
+- **`tokensHash`** is a single coarse hash of the whole token set. Per-token diff
+  granularity is a deliberate later refinement (start coarse, refine if consumers ask).
+- **`schemaVersion`** governs hash stability: any extractor change that would alter
+  existing hashes *without* a real design change must bump it, so a consumer can tell
+  a re-canonicalisation apart from a genuine design move. It is distinct from
+  `designVersion` (the package/tag version) and from the component schema's own shape.
+- **`generatedAt`** is informational and never hashed; it is reused from the prior
+  manifest when nothing hashed changed, so a no-op `make ir` produces no git churn.
+
+The downstream consumer `drift` check (WHYNOT-WP-0003 T05) compares a target
+manifest against the consumer's adopted `.whynot-design.lock` and reports added /
+changed / removed components plus token changes — the mirror of the upstream adapter
+drift, sharing the `0` ok · `3` drift exit-code convention.
+
 ## Tokens — `ir/tokens.json`
 
 Adopts the **W3C Design Tokens Community Group** format: every token is an object