feat: add doc-guardian plugin for documentation lifecycle management

Adds automatic documentation drift detection and synchronization:
- PostToolUse hook detects when code changes affect docs
- Stop hook reminds of pending updates before session ends
- /doc-audit command for full project documentation scan
- /doc-sync command to batch apply pending updates
- doc-analyzer agent for cross-reference analysis
- doc-patterns skill for documentation structure knowledge

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

plugins/doc-guardian/README.md

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+# doc-guardian
+
+Automatic documentation drift detection and synchronization for Claude Code projects.
+
+## Problem Solved
+
+Documentation gets outdated. Functions get renamed, configs change, versions bump—but docs lag behind. This creates:
+- Multiple review cycles finding stale references
+- Unnecessary commits fixing docs piecemeal
+- User confusion from outdated instructions
+
+## Solution
+
+doc-guardian watches your code changes and automatically:
+1. Detects when changes affect documentation
+2. Queues updates silently (doesn't interrupt your flow)
+3. Syncs all doc changes in a single commit when ready
+
+## Commands
+
+| Command | Description |
+|---------|-------------|
+| `/doc-audit` | Full project scan - reports all drift without changing anything |
+| `/doc-sync` | Apply all pending documentation updates in one commit |
+
+## Hooks
+
+- **PostToolUse (Write\|Edit)**: Silently checks if code changes affect docs
+- **Stop**: Reminds you of pending doc updates before session ends
+
+## What It Detects
+
+- **Broken References**: Function/class renamed but docs still use old name
+- **Version Drift**: Python 3.9 in docs but 3.11 in pyproject.toml
+- **Missing Docs**: Public functions without docstrings
+- **Stale Examples**: CLI examples that no longer work
+
+## Installation
+
+This plugin is part of the claude-code-marketplace.
+
+```bash
+/plugin marketplace add https://gitea.hotserv.cloud/personal-projects/support-claude-mktplace.git
+/plugin install doc-guardian
+```
+
+## Integration
+
+See claude-md-integration.md for CLAUDE.md additions.