v2.3.0 — version bump + dependency refresh + action updates

Includes:
- Client-go v2.42.0 -> v2.43.0 (webhook payload struct additions only;
  no MCP code changes needed)
- Go modules: golang.org/x/tools 0.46.0 -> 0.47.0, lufia/plan9stats
- pnpm: astro 7.0.3, astro-mermaid 2.1.0, eslint 10.6.0, mermaid 11.16.0,
  prettier 3.9.1, @astrojs/starlight 0.41.1, etc.
- Alpine 3.24.0 -> 3.24.1 (Dockerfile runtime stage)
- actions/checkout v6 -> v7 (4 workflow files)
- CLAUDE.md client-go version aligned with go.mod
- Dropped duplicate CE-on-Enterprise meta eval section
- Audit_doc_coverage auditor (DOC-002, PR #192)

Full release notes in CHANGELOG and the release PR body.