feat(mcp): add list_tasks(workstream_id) tool — resolves FR 7074fd47

Agents had no way to look up task UUIDs by workstream; they were stuck
unable to call update_task_status without already knowing the UUID.
list_tasks() wraps GET /tasks with workstream_id filter, returning
[{id, title, status, priority}] for all matching tasks.

FR raised by kaizen-agentic worker on COULOMBCORE while syncing
KAIZEN-WP-0002 task IDs. Marked merged in contributions.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

mcp_server/server.py

@@ -273,6 +273,21 @@ def get_topic(slug: str) -> str:
     return json.dumps({"topic": topic_detail, "recent_progress": recent}, indent=2)
 
 
+@mcp.tool()
+def list_tasks(workstream_id: str, status: str | None = None) -> str:
+    """List all tasks in a workstream, optionally filtered by status.
+
+    Args:
+        workstream_id: UUID of the workstream (required).
+        status: Optional filter — todo | in_progress | blocked | done | cancelled.
+
+    Returns [{id, title, status, priority, assignee, due_date, needs_human}] for every
+    matching task. Use this to look up task UUIDs before calling update_task_status,
+    or to check which tasks from a workplan file are already synced to the DB.
+    """
+    return json.dumps(_get("/tasks", {"workstream_id": workstream_id, "status": status}), indent=2)
+
+
 @mcp.tool()
 def list_blocked_tasks(workstream_id: str | None = None) -> str:
     """List all tasks with status=blocked, optionally filtered by workstream_id."""