Mark skills as not user-invocable

Skills are knowledge modules referenced by commands, not
directly invoked by users. Added user-invocable: false to:
- backlog-grooming (used by /groom)
- claude-md-writing (used by /update-claude-md)
- code-review (used by /review-pr)
- issue-writing (used by /create-issue)
- roadmap-planning (used by /plan-issues)
- vision-management (used by /vision, /manifesto)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

skills/backlog-grooming/SKILL.md

@@ -1,6 +1,7 @@
 ---
 name: backlog-grooming
 description: Review and improve existing issues for clarity and actionability. Use when grooming the backlog, reviewing issue quality, cleaning up stale issues, or when the user wants to improve existing issues.
+user-invocable: false
 ---
 
 # Backlog Grooming

skills/claude-md-writing/SKILL.md

@@ -1,6 +1,7 @@
 ---
 name: claude-md-writing
 description: Write effective CLAUDE.md files that give AI assistants the context they need. Use when creating new repos, improving existing CLAUDE.md files, or setting up projects.
+user-invocable: false
 ---
 
 # Writing Effective CLAUDE.md Files

skills/code-review/SKILL.md

@@ -1,6 +1,7 @@
 ---
 name: code-review
 description: Review code for quality, bugs, security, and style issues. Use when reviewing pull requests, checking code quality, looking for bugs or security vulnerabilities, or when the user asks for a code review.
+user-invocable: false
 ---
 
 # Code Review

skills/issue-writing/SKILL.md

@@ -1,6 +1,7 @@
 ---
 name: issue-writing
 description: Write clear, actionable issues with proper structure and acceptance criteria. Use when creating issues, writing bug reports, feature requests, or when the user needs help structuring an issue.
+user-invocable: false
 ---
 
 # Issue Writing

skills/roadmap-planning/SKILL.md

@@ -1,6 +1,7 @@
 ---
 name: roadmap-planning
 description: Plan features and break down work into implementable issues. Use when planning a feature, creating a roadmap, breaking down large tasks, or when the user needs help organizing work into issues.
+user-invocable: false
 ---
 
 # Roadmap Planning

skills/vision-management/SKILL.md

@@ -1,6 +1,7 @@
 ---
 name: vision-management
 description: Create, maintain, and evolve organization manifesto and product visions. Use when working with manifesto.md, vision.md, milestones, or aligning work with organizational direction.
+user-invocable: false
 ---
 
 # Vision Management