chore: add node-pty/xterm deps, tmux in Docker, dashboard_runs.tmux_session column

server/db.js

@@ -248,7 +248,7 @@ db.exec(`
   CREATE TABLE IF NOT EXISTS dashboard_runs (
     id TEXT PRIMARY KEY,
     session_id TEXT,
-    mode TEXT NOT NULL,
+    mode TEXT,
     cwd TEXT NOT NULL,
     model TEXT,
     permission_mode TEXT,
@@ -496,6 +496,15 @@ try {
 }
 db.prepare("CREATE INDEX IF NOT EXISTS idx_dashboard_runs_lane ON dashboard_runs(lane_id)").run();
 
+// Migrate: tmux session name backing this run (tmux+PTY terminal design,
+// 2026-08-11). Additive and nullable — historical rows spawned via the old
+// stream-json mode have no tmux session and are display-only history now.
+try {
+  db.prepare("SELECT tmux_session FROM dashboard_runs LIMIT 1").get();
+} catch {
+  db.prepare("ALTER TABLE dashboard_runs ADD COLUMN tmux_session TEXT").run();
+}
+
 // Migrate: add stage-detection columns to lanes. Inference is never evidence —
 // these are additive columns separate from `stage` (the declared stage), so
 // `stage`'s meaning is untouched and turning the feature off loses nothing.