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/TOOLS.md

@@ -27,6 +27,7 @@ Do not use them as a substitute for formal work definition inside the domain rep
 | `get_domain_summary(domain_slug)` | `domain_slug`: e.g. `"railiance"` | **Domain session start.** Scoped snapshot: active workstreams, blocking decisions, last 5 events, repo SBOM status — ~10% of get_state_summary() token cost. |
 | `get_state_summary()` | — | **Cross-domain work / custodian sessions.** Full snapshot: totals, all blocking decisions, all blocked tasks, all open workstreams, last 20 events. Large (~10k tokens). |
 | `get_topic(slug)` | `slug`: e.g. `"markitect"` | Deep-dive on one topic + its workstreams + recent events. |
+| `list_tasks(workstream_id, status?)` | `workstream_id`: UUID (required); `status?`: todo/in_progress/blocked/done/cancelled | List all tasks in a workstream. Use this to look up task UUIDs before calling `update_task_status`, or to verify which workplan tasks are already synced to the DB. |
 | `list_blocked_tasks(workstream_id?)` | optional filter | Surface all impediments, optionally scoped to one workstream. |
 | `list_pending_decisions(topic_id?)` | optional filter | Decisions holding up work, sorted by deadline. |
 | `get_recent_progress(limit, since?)` | `limit` default 20; `since` ISO datetime | Reconstruct recent session history. |