fix(runs): persist tmux-backed runs so a resumed session shows its own info

`dashboard_runs.mode` is NOT NULL and `recordRun` swallows insert errors by
design, so pty-run.js passing `mode: null` meant NO tmux-backed run was ever
persisted — the newest row in a live database dated from before pty-run.js
replaced run-spawner.js. `publicRun` reads cwd, model, prompt preview,
started_at and session_id off that row and the handle itself is recomputed
from tmux, so the runs modal rendered a live row with no cwd, no model, no
prompt and a start date of Jan 1 1970. The same missing row is why a resumed
session kept its separate `external` badge: the client dedupes an external
session against the session ids carried by run rows, and no run row ever
carried one.

- pty-run.js records `mode: "interactive"` — every run here is one pane.
- dashboard-runs.js still never fails a live run on a db error, but warns
  instead of swallowing silently; that silence hid this for six weeks.
- RunHistory renders `startedAt: 0` as "-" rather than dating a row with no
  known start time to the epoch.

Also closes the other half of the same lie: adopting a pane that is already
running an agent now throws ERUNLIVE (409 from both the lane start action and
POST /api/run) when the request carried a prompt or a resumeSessionId. That
argv cannot be typed over a live agent, so answering 200 reported a resume
that never spawned. A start asking for nothing but a pane still adopts.

server/lib/dashboard-runs.js

@@ -91,8 +91,12 @@ function recordRun(handle) {
       lane_id: typeof handle.laneId === "number" ? handle.laneId : null,
       tool: handle.tool === "codex" ? "codex" : "claude",
     });
-  } catch {
-    /* persistence is best-effort */
+  } catch (err) {
+    // Best-effort by design (a live run must never fail because sqlite did),
+    // but not silent: a swallowed insert leaves the runs modal showing rows with
+    // no cwd, model, prompt or start time, which reads as a UI bug rather than a
+    // persistence one. Say it once, here, where the cause is known.
+    console.warn(`[dashboard-runs] failed to record run ${handle?.id}: ${err.message}`);
   }
 }