Add new frontmatter fields from Claude Code 2.1.0

Update documentation and apply new frontmatter capabilities:

Documentation:
- Add user-invocable, context, agent, hooks fields to writing-skills.md
- Add disallowedTools, permissionMode, hooks fields to writing-agents.md
- Add model, context, hooks, allowed-tools fields to writing-commands.md
- Document skill hot-reload, built-in agents, background execution

Skills:
- Add user-invocable: false to gitea (CLI reference)
- Add user-invocable: false to repo-conventions (standards reference)

Commands:
- Add context: fork to heavy exploration commands (improve, plan-issues,
  create-repo, update-claude-md)
- Add missing argument-hint to roadmap, manifesto, improve

Agents:
- Add disallowedTools: [Edit, Write] to code-reviewer for safety

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

commands/create-repo.md

@@ -1,6 +1,7 @@
 ---
 description: Create a new repository with standard structure. Scaffolds vision.md, CLAUDE.md, and CI configuration.
 argument-hint: <repo-name>
+context: fork
 ---
 
 # Create Repository

commands/improve.md

@@ -1,5 +1,7 @@
 ---
 description: Identify improvement opportunities based on product vision. Analyzes gaps between vision goals and current backlog.
+argument-hint:
+context: fork
 ---
 
 # Improvement Analysis

commands/manifesto.md

@@ -1,5 +1,6 @@
 ---
 description: View and manage the organization manifesto. Shows identity, personas, beliefs, and principles.
+argument-hint:
 ---
 
 # Organization Manifesto

commands/plan-issues.md

@@ -1,6 +1,7 @@
 ---
 description: Plan and create issues for a feature or improvement. Breaks down work into well-structured issues with vision alignment.
 argument-hint: <feature-description>
+context: fork
 ---
 
 # Plan Feature: $1

commands/roadmap.md

@@ -1,5 +1,6 @@
 ---
 description: View current issues as a roadmap. Shows open issues organized by status and dependencies.
+argument-hint:
 ---
 
 # Roadmap View

commands/update-claude-md.md

@@ -1,6 +1,7 @@
 ---
 description: Update or create CLAUDE.md with current project context. Explores the project and ensures organization context is present.
 argument-hint:
+context: fork
 ---
 
 # Update CLAUDE.md