fix(doc-guardian): use passive wording and add debouncing to reduce interruptions

The PostToolUse hook was causing workflow interruptions because:
1. Actionable language ("update needed") triggered Claude to seek confirmation
2. Rapid edits (4+ in sequence) generated multiple notifications

Changes:
- Message changed from "update needed" to "drift queued" (passive, informational)
- Added 5-second debouncing: same-type edits within window are silently queued
- Added queue clearing step to doc-sync.md command

Note: Issue #287 also mentions URL restriction behavior, but this was not
found in the current codebase - may have been a different component or
already fixed. Marking as partial fix.

Fixes #287

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

plugins/doc-guardian/commands/doc-sync.md

@@ -52,7 +52,13 @@ Then proceed with the sync.
    - Single commit: `docs: sync documentation with code changes`
    - Include summary of what was updated in commit body
 
-5. **Output**
+5. **Clear Queue**
+   After successful sync, clear the queue file:
+   ```bash
+   echo "# Doc Guardian Queue - cleared after sync on $(date +%Y-%m-%d)" > .doc-guardian-queue
+   ```
+
+6. **Output**
 ```
 ## Documentation Sync Complete