loops: repo picker + agent/team/org staffing + sidebar edit/delete

Adds the missing pieces the wizard needed and the sidebar controls
around it:

- LoopsWizard is now a 6-step flow (identity → repo → task/topology
  → triggers → repeat → assign agents) plus the existing secrets
  card. ResearchWizard picks up the same repo step and a hard gate
  when the workspace has zero agents.
- New LoopStaffingStep with three tabs — Individual / Team /
  Organization — that mix freely per loop; selections persist via
  new loop_agents / loop_teams / loop_orgs join tables (0035
  migration), each cascading on loop_id so hard-delete stays a
  single-row DELETE.
- Backend CreateLoopRequest / UpdateLoopRequest accept the three
  lists and apply_staffing does a transactional replace-all;
  list_loops / get_loop hydrate the lists via a flattened
  LoopWithStaffing response.
- LoopsList sidebar gains per-row enable/disable, edit (reopens the
  wizard prefilled with the current loop, PATCHes on submit), and
  delete with an inline confirm.
- NoAgentsGate blocks launching a loop or research topic from a
  workspace with no roster; the sidebar `+` buttons also disable
  with a tooltip pointing at the TEAM tier.

Not yet wired: the run driver still fills role slots from the
workspace-wide pool; teaching enqueue_iteration to prefer
loop_agents/loop_teams/loop_orgs is a follow-up.

.sqlx/query-c73f821ea00857bcc06add6478a4f999bbf8bdecb96e9fb79cdeafd1d22a2a2f.json

@@ -0,0 +1,14 @@
+{
+  "db_name": "PostgreSQL",
+  "query": "DELETE FROM loop_teams WHERE loop_id = $1",
+  "describe": {
+    "columns": [],
+    "parameters": {
+      "Left": [
+        "Uuid"
+      ]
+    },
+    "nullable": []
+  },
+  "hash": "c73f821ea00857bcc06add6478a4f999bbf8bdecb96e9fb79cdeafd1d22a2a2f"
+}