refactor(tui): resume rows fold titles only, timestamp from artifact mtime

Rows no longer read logs for anything but the batch title fold: the
activity timestamp is a live session's last in-memory event time or the
artifact mtime via the optional sessionPersistence.locate(), falling
back to creation time; the last-turn, route, and goal columns are gone.
Route availability moves to the Enter-time preflight, which already
fully reads and replay-validates the one chosen log. The projectSessions
public API this PR had added to session-query is reverted — the change
is now confined to the TUI package.

packages/ui/tui/tests/tui.snapshot.ts

@@ -879,12 +879,12 @@ describe('TUI terminal-state snapshots', () => {
         { type: 'step/end', seq: 5, time: Date.parse(`${day}T00:00:06Z`), data: { turn: 1, step: 1 } },
         { type: 'turn/end', seq: 6, time: Date.parse(`${day}T00:00:07Z`), data: { turn: 1, reason: { kind: 'completed' } } },
         { type: 'session/title', seq: 7, time: Date.parse(`${day}T00:00:08Z`), data: { title, messageSeqs: [1], source: { kind: 'fallback' } } },
-        // A prior pickup, dated well after the work: the picker must still
-        // show the work's date, not the pickup's.
-        { type: 'session/end-seed', seq: 8, time: Date.parse('2026-07-23T07:59:00.000Z'), data: {} },
       ],
     })
     const listGate = Promise.withResolvers<undefined>()
+    // Rows show metadata activity (here the created-at fallback: the fake
+    // store locates no per-session artifact to stat) plus each log's one
+    // batch-folded title; nothing else is read from the logs.
     const harness = await setupSnapshot({
       sessionPersistence: {
         list: async () => {