Fix MCP update tool bypassing close approval workflow

- Detect when update is called with status='closed'
- Redirect to close_issue to preserve approval workflow
- Ensures closing tasks always requires same approval regardless of tool used

Fixes #90

Amp-Thread-ID: https://ampcode.com/threads/T-9eab3a82-18f3-4ae3-a2d5-d114811383c1
Co-authored-by: Amp <amp@ampcode.com>

integrations/beads-mcp/src/beads_mcp/server.py

@@ -339,6 +339,11 @@ async def update_issue(
     workspace_root: str | None = None,
 ) -> Issue:
     """Update an existing issue."""
+    # If trying to close via update, redirect to close_issue to preserve approval workflow
+    if status == "closed":
+        issues = await beads_close_issue(issue_id=issue_id, reason="Closed via update")
+        return issues[0] if issues else None
+    
     return await beads_update_issue(
         issue_id=issue_id,
         status=status,