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>

CHANGELOG.md

@@ -8,6 +8,26 @@ Format follows [Keep a Changelog](https://keepachangelog.com/en/1.1.0/). Version
 
 ### Added
 
+- **Versioned IR manifest + consumer drift-check** (WHYNOT-WP-0003, Phase 1–4). The
+  `ir/` contract is now the unit of versioned downstream consumption:
+  - `ir/manifest.json` (T03) — per-version inventory + diff anchor:
+    `{ schemaVersion, designVersion, generatedAt, tokensHash, components:[{name,group,hash}] }`,
+    each hash a deterministic sha256 over canonicalised JSON (formatting-invariant,
+    `generatedAt` reused on no-op runs → no git churn). Schema:
+    `ir/schema/manifest.schema.json`. Emitted by `make ir`.
+  - `ir/INDEX.md` (T07) — human-readable catalog generated from the contracts;
+    browse a version without cloning or running anything. Emitted by `make ir`.
+  - **`npx @whynot/design drift`** (T05) — consumer-side drift-check (`bin/whynot-design.mjs`,
+    new `bin` entry). Compares a consumer's adopted `.whynot-design.lock` against the
+    installed package's manifest and reports added/changed/removed components + token
+    changes (`--json`, `--update`, `--manifest`, `--version`, `--lock`). Exit codes
+    mirror the adapter contract: `0` in sync · `2` usage error · `3` drift.
+  - `.whynot-design.lock` sync-point format (T04) — `ir/schema/lock.schema.json` +
+    documented lifecycle (consumer-side mirror of `designbook/.design-sync.json`).
+  - `CONSUMING.md` (T06) — pin → inspect → drift → update guide, with a runnable
+    `examples/consumer-fixture/`; cross-linked from `README.md` and `MultiFrameworkSupport.md`.
+  - `CONSUMER_CONTRACT_PARITY.md` (T09) — design-only note + recorded go/defer
+    decision for the heavier live-UI-vs-contract parity mode (deferred).
 - **Publishable to the coulomb Gitea npm registry** (WHYNOT-WP-0003 T02) — `private:false`,
   `publishConfig.registry`, real `repository.url`, an `.npmrc` scope + `${NPM_AUTH_TOKEN}`
   reference (no secret committed), and `PUBLISHING.md` (publish flow + consumer install +