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/harness.ts

@@ -69,6 +69,8 @@ export interface TuiHarnessOptions {
   sessionPersistence?: {
     list(): Promise<SessionHeader[]>
     load?(id: ReturnType<typeof SessionId>): Promise<{ meta: SessionHeader; events: Session['events'] }>
+    /** Per-session artifact location for mtime-based activity; defaults to none. */
+    locate?(meta: SessionHeader): { kind: string; path: string } | undefined
   }
   handoffResume?: TuiRuntime['handoffResume']
   /** Host-supplied exit line; absent exercises the no-message path. */
@@ -156,7 +158,7 @@ export async function createTuiTestHarness<TerminalType extends Terminal, Exit e
     const persistence = options.sessionPersistence
     ctx.provide('sessionPersistence', {
       ...persistence,
-      locate: () => undefined,
+      locate: (meta: SessionHeader) => persistence.locate?.(meta),
       create: () => Promise.resolve(),
       append: () => Promise.resolve(),
       load: persistence.load === undefined