feat(#1430): versioned capability manifest + native stamping (ADR-1244 Phase 1) (#1436)

* feat(#1430): versioned capability manifest + native stamping (ADR-1244 Phase 1)

Make the capability manifest versioned — the data substrate the Capability
Ecosystem (ADR-1244) keys off:

- capability.json gains a REQUIRED semver `version` plus the optional
  ecosystem envelope (`engines.gsd`, `compatVersions`, `integrity`,
  `provenance`); the build-time conformance validator enforces them via a new
  `validateVersionEnvelope()` (exported for the Phase 2 runtime overlay).
- All 32 native capabilities stamped with `version` (= package version,
  lockstep) + `engines.gsd`; `sync-manifest-versions.cjs` gains a glob sweep
  that keeps them in sync, and the issue-844 regression guard is extended.
- Strict SemVer 2.0.0 grammar blocks metacharacter/space/unicode smuggling in
  version strings; range/integrity fields are shape-validated (satisfaction
  and the load-time gate are deferred to Phase 2/4).
- Capability rel-paths emitted forward-slash for cross-platform git correctness.

Closes #1430

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

* docs(#1430): add changeset for versioned capability manifest

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

---------

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

.changeset/kind-dogs-dart.md

@@ -0,0 +1,5 @@
+---
+type: Added
+pr: 1436
+---
+**Capability manifests are now versioned** — every `capability.json` carries a required semver `version`, plus optional `engines.gsd`, `compatVersions`, `integrity` and `provenance` fields, enforced by the capability conformance validator. First-party capabilities are version-stamped in lockstep with the GSD release. Foundation (ADR-1244 Phase 1) for installing, upgrading, and removing capabilities in later releases.