research sidebar: delete-with-confirm per topic

Mirror the row-level delete affordance the loops sidebar already
has. Loops was wired earlier; research had a bare title-only card
with no way to remove a stale topic.

- cm-db: research_topics::delete cascades via existing FK rules
  (research_topic_agents, research_publish_approvals, and the new
  research_outcomes all CASCADE on topic_id; topology_runs's
  research_topic_id back-ref is SET NULL so historical runs stay).
- cm-api: DELETE /api/research/{id} → 204. Idempotent.
- Frontend: deleteTopic helper. ResearchList row is now a card
  with the existing title/status/outcome header plus a trash icon
  that flips the card into an inline "Delete topic + all outcomes?"
  confirm strip. Confirm → red Delete / gray Cancel. If the
  deleted topic was selected, selection clears; local counter
  bumps the list refetch without waiting on a parent.

.sqlx/query-60c65d67613db839401ebab66eb28710e292d7bec1debef316634ef735bc48ff.json

@@ -0,0 +1,15 @@
+{
+  "db_name": "PostgreSQL",
+  "query": "DELETE FROM research_topics WHERE id = $1 AND workspace_id = $2",
+  "describe": {
+    "columns": [],
+    "parameters": {
+      "Left": [
+        "Uuid",
+        "Uuid"
+      ]
+    },
+    "nullable": []
+  },
+  "hash": "60c65d67613db839401ebab66eb28710e292d7bec1debef316634ef735bc48ff"
+}