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>

docs/how-to/version-a-capability.md

@@ -28,6 +28,8 @@ Set the version in your manifest before every release:
 }
 ```
 
+> **First-party capabilities are versioned automatically.** The native capabilities shipped inside GSD (`capabilities/<id>/capability.json`) are stamped in lockstep with the GSD package version at release time by `scripts/sync-manifest-versions.cjs` — their `version` always equals the GSD version, so per-capability semver and `compatVersions` only carry independent signal for **third-party** capabilities. As an author of a third-party capability, you own your own version line; the lockstep rule does not apply to you.
+
 ### Decide when to raise `engines.gsd`
 
 The `engines.gsd` range expresses which GSD host versions your capability is compatible with. GSD enforces this as a hard gate at install time and again at load time.
@@ -137,5 +139,5 @@ If the new version of a capability requires a GSD version newer than what you ha
 
 - [How to remove or disable a capability](remove-a-capability.md)
 - [Develop a Capability for GSD 1.5+](develop-a-capability.md)
-- [Capability manifest reference](../reference/capability-matrix.md)
+- [Capability manifest reference](../reference/capability-manifest.md)
 - [Turn a capability off (and keep it off)](turn-a-capability-off.md)