…-build time (ADR-0081) (#2485)

Wire the spec↔frontend react-block conformance check in as a baseline ratchet at
the one place the registry-inputs manifest is produced for free —
`scripts/build-console.sh`, right after it dumps `sdui.manifest.json`. Running it
on every framework PR isn't worth it (the manifest only exists at console-build
time); the ratchet catches NEW divergence there at near-zero marginal cost.

- check-react-blocks-conformance.ts gains `--baseline <path>` (compare, report
  only regressions: a component exposing a NEW undocumented prop or a
  previously-present block vanishing) and `--update` (accept current as the new
  baseline). The soft spec-only signal is not gated. `--strict` exits 1 on
  regression.
- packages/spec/react-conformance.baseline.json captures the accepted state
  (ListView frontend-only fields/options, ObjectChart data; rest clean after
  #2113/#2484).
- build-console.sh runs the ratchet warn-only after the dump — never fails the
  console build, surfaces new divergence at the release point.
- audit doc documents the ratchet + how to re-accept the baseline.

Co-authored-by: Jack Zhuang <277994282+os-zhuang@users.noreply.github.com>
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

Records the model that the spec↔contract↔conformance↔prop-gate work converged
on (now implemented + merged across framework #2478/#2480/#2482/#2484/#2485/#2488/
#2489 and objectui #2113/#2115), so future contributors don't re-litigate it:

- the spec zod schema is the protocol source of truth; the AI-facing contract is
  GENERATED from it (zero-drift), never hand-authored;
- registry inputs are the designer palette (a curated subset) — spec-only is a
  soft signal, frontend-only is the actionable one;
- React-interaction props (callbacks/controlled/binding escape-hatches) live in a
  thin overlay, not the spec; declaring a genuine binding there is how a
  frontend-only prop is closed (baseline now 0 frontend-only);
- conformance is a build-time baseline ratchet (build-console.sh, warn-only),
  not a per-PR gate — the manifest only exists at console-build time;
- authoring correctness is a hard gate at os validate (missing-required = error,
  typo = warning); and the dogfood golden page proves the chain closes.

Captures the alternatives rejected (copy props into spec / per-PR hard gate /
hand-authored contract / registry-as-source).

Co-authored-by: Jack Zhuang <277994282+os-zhuang@users.noreply.github.com>
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>