chore: prepare release v0.4.0 (#208)

## Summary

Version bump to v0.4.0 — documentation-focused release closing 11 gaps
vs official Claude Code docs.

## Changes

### Added
- Output styles reference for plugin-structure skill
- Permission modes & rules reference for agent-development skill

### Documentation
- Closed 11 documentation gaps vs official Claude Code docs (output
styles, permission modes, agent teams, context management, memory
system, hook debugging, MCP features, enterprise settings, skill
substitutions, plugin validation)
- Updated trigger phrases across 4 skills for improved discoverability

### Dependencies
- Bump anthropics/claude-code-action to v1.0.48 (from v1.0.34)
- Bump actions/cache to v5.0.3
- Bump reviewdog/action-actionlint to v1.70.0

### Maintenance
- Update claude-pr-review model to opus 4.6
- Update .gitignore with additional exclusions

## Checklist

- [x] Version updated in plugin.json, marketplace.json, CLAUDE.md
- [x] CHANGELOG.md updated with release notes
- [x] Markdownlint passes (0 errors)
- [x] Shellcheck passes (info-level only)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: sjnims

CHANGELOG.md

@@ -7,7 +7,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
-## [0.4.0] - 2026-02-09
+## [0.4.0] - 2026-02-10
 
 ### Added
 
@@ -29,6 +29,18 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   - **Plugin validation** (GAP 10): `--verbose` flag for plugin loading diagnostics
 - **Updated trigger phrases** across plugin-structure, agent-development, skill-development, and mcp-integration skills for improved discoverability
 - **Expanded manifest reference** with `outputStyles` field documentation
+- **Updated skill and command counts** in CLAUDE.md and CONTRIBUTING.md
+
+### Dependencies
+
+- Bump anthropics/claude-code-action to v1.0.48 (from v1.0.34)
+- Bump actions/cache to v5.0.3 (#206)
+- Bump reviewdog/action-actionlint to v1.70.0 (#206)
+
+### Maintenance
+
+- Update claude-pr-review model to opus 4.6
+- Update .gitignore with additional exclusions
 
 ## [0.3.4] - 2026-01-30