docs(CLAUDE.md): update Available Skills to reflect current state

Removed outdated skills that haven't been migrated from old/ directory:
- /manifesto, /vision, /work-issue, /dashboard, /review-pr
- /create-issue, /retro, /plan-issues, /groom

Added current user-invocable skills:
- /vision-to-backlog
- /create-milestones
- /spawn-issues
- /create-capability
- /capability-writing

This prevents confusion when users try non-existent skills, which could
cause the system to fall back to base instructions (using gh instead of tea).

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

CLAUDE.md

@@ -52,15 +52,11 @@ See the manifesto for our identity, personas, and beliefs about AI-augmented dev
 
 | Skill | Description |
 |-------|-------------|
-| `/manifesto` | View/manage organization manifesto |
-| `/vision` | View/manage product vision and milestones |
-| `/work-issue <n>` | Fetch issue, create branch, implement, create PR |
-| `/dashboard` | Show open issues and PRs |
-| `/review-pr <n>` | Review PR with diff and comments |
-| `/create-issue` | Create single or batch issues |
-| `/retro` | Capture learnings as issues for encoding |
-| `/plan-issues` | Break down features into issues |
-| `/groom` | Improve issue quality |
+| `/vision-to-backlog [vision-file]` | Transform product vision into executable backlog via DDD |
+| `/create-milestones` | Organize issues into value-based milestones |
+| `/spawn-issues <n> [<n>...]` | Implement multiple issues in parallel with automated review |
+| `/create-capability` | Create new skill, agent, or capability for the architecture |
+| `/capability-writing` | Guide for designing capabilities following best practices |
 
 ## Gitea Integration