fix(release): guard Claude Code integration version

[ijevin]

Summary

• release the pending Claude Code integration changes as plugin version 0.7.6
• add a read-only release-integration.sh --check preflight for manifest/tag/unreleased-change consistency
• block core releases before mutation or tagging when Claude Code integration changes have not been released
• regenerate the docs skill during core releases so its bundled OpenAPI copy cannot drift
• add an isolated regression test for stale changes, manifest mismatch, nested marketplace version keys, extra arguments, the core-release gate, and the docs-skill generation chain

Why 0.7.6, not 0.8.5

Integrations have been independently versioned since #565. The latest Claude Code integration release is integrations/claude-code/v0.7.5, so the next integration version is 0.7.6; coupling it to the core v0.8.5 tag would break that contract.

The immediate bug was that #2801 changed the Claude Code integration, but no integration release followed. Both plugin manifests therefore stayed at 0.7.5, causing claude plugin update hindsight-memory@hindsight to treat the cached plugin as current.

The new preflight preserves independent integration releases: it is read-only and only blocks a core release when Claude Code has commits after its latest integration tag, when the plugin and marketplace manifests disagree, or when the manifest version does not match the latest integration tag.

The first CI run also exposed an existing release-pipeline gap: core v0.8.5 regenerated hindsight-docs/static/openapi.json but did not refresh skills/hindsight-docs/references/openapi.json, leaving the bundled copy at v0.8.4. The core release flow now runs generate-docs-skill.sh after OpenAPI/client generation, and this PR synchronizes the stale generated copy.

Testing

• bash scripts/tests/test-release-integration.sh
• cd hindsight-integrations/claude-code && uv run --quiet pytest tests/ -q (206 passed)
• ./scripts/generate-docs-skill.sh followed by a clean generated-files check
• bash -n scripts/release-integration.sh
• bash -n scripts/release.sh
• bash -n scripts/tests/test-release-integration.sh
• JSON validation for both manifests and the bundled OpenAPI spec
• byte-for-byte comparison of the source and bundled OpenAPI specs
• git diff --check upstream/main...HEAD

No uv.lock files or advisory locks are included.

Fixes #2900