research: pipeline-running signal + spinners so users aren't guessing

The prior flow was ambiguous: after hitting Start research, status
flipped to "processing" and a "Submit for review" button appeared
immediately with no indication that anything was actually running.
Users had to guess whether the pipeline was working or stalled.

Backend surfaces the truth as a signal:
- new topology_runs::active_runs_for_research_topic counts
  queued+running runs whose research_topic_id matches
- TopicDetail includes runs_in_flight: i64 alongside the existing
  status field, so the canvas can distinguish "pipeline still
  working" from "runner stalled".

ResearchCanvas is now honest about state:
- while runs_in_flight > 0, the header status pill grows a cyan
  "N runs in flight" badge with an inline SVG spinner
- the stage-explainer card turns cyan-bordered and shows a
  "pipeline is running" hint, plus copy pointing the user at the
  Agents tier where each teammate's activity streams live
- the "Submit for review (manual)" button is HIDDEN while any run
  is in flight — it's an escape hatch for stalled runs only, not
  the happy-path action. It reappears if runs_in_flight drops to
  zero but the topic is still marked processing, so a stalled
  runner can still be nudged along.
- the canvas polls getTopic every 4s while status is processing/
  publishing or runs_in_flight > 0, so the spinner + outcome swap
  in automatically when the pipeline completes.

ResearchList sidebar:
- each row's status dot becomes a spinner when the topic's status
  is processing or publishing, matching the canvas at a glance
- the list also polls every 6s while ANY topic is active, so
  transitions land in the sidebar without waiting on a parent bump.
  The poll is gated on a derived boolean to avoid effect thrash.

Follow-up: same pattern belongs on LoopsList / LoopsCanvas for
loop iterations in flight — same signal (queued+running runs per
loop) but not wired here.

.sqlx/query-a014c185ae37744045471dfbb4d82f783f23177c4e53bc1348f3384be446aecd.json

@@ -0,0 +1,22 @@
+{
+  "db_name": "PostgreSQL",
+  "query": "SELECT count(*) AS n\n           FROM topology_runs\n          WHERE research_topic_id = $1\n            AND status IN ('queued', 'running')",
+  "describe": {
+    "columns": [
+      {
+        "ordinal": 0,
+        "name": "n",
+        "type_info": "Int8"
+      }
+    ],
+    "parameters": {
+      "Left": [
+        "Uuid"
+      ]
+    },
+    "nullable": [
+      null
+    ]
+  },
+  "hash": "a014c185ae37744045471dfbb4d82f783f23177c4e53bc1348f3384be446aecd"
+}