fix(desktop): restored background tabs resolve their session title without a click

A restored session tile has no runtimeId and never mounts its pane until first
activation, so the by-id resolution effect inside SessionTilePane never runs.
When the row is also outside the recents page and project tree, tileTitle()
falls back to "New session" until the user clicks the tab (#94167).

Add a one-shot backfill, wired next to watchSessionTiles(): once the gateway
is open, look each unrestored, untitled, unlisted tile up via
resolveStoredSession(id, tile.ownerRoute). That call already upserts the row
into $sessions, which the tab strip watches, so the tab renames itself —
nothing new is persisted and workspaceTabTitle stays the Bot Chat marker.

Live repro (Electron e2e, target session pushed off the 50-row recents page
by 60 newer sessions, restored as a stacked background tab): main showed
"New session" after boot with no click; with this fix the tab reads the real
title while the pane is still unmounted.

Closes #94167
Supersedes #94212

Co-authored-by: 686f6c61 <github@00b.tech>

apps/desktop/src/app/chat/session-tile.test.ts

@@ -1,6 +1,9 @@
-import { describe, expect, it } from 'vitest'
+import { afterEach, describe, expect, it, vi } from 'vitest'
 
-import { sessionTileResumeFailure } from './session-tile'
+import { $gatewayState, $sessions, setSessions } from '@/store/session'
+import { $sessionTiles } from '@/store/session-states'
+
+import { sessionTileResumeFailure, startUnrestoredTileTitleBackfill } from './session-tile'
 
 describe('sessionTileResumeFailure', () => {
   it('keeps a confirmed durable session retryable instead of repeating a stale 404', () => {
@@ -17,3 +20,43 @@ describe('sessionTileResumeFailure', () => {
     expect(sessionTileResumeFailure('session not found', true, false)).toBeUndefined()
   })
 })
+
+describe('startUnrestoredTileTitleBackfill (#94167)', () => {
+  afterEach(() => {
+    $gatewayState.set('idle')
+    $sessionTiles.set([])
+    setSessions([])
+  })
+
+  it('backfills unlisted unrestored tiles by id via their ownerRoute once the gateway opens', async () => {
+    const ownerRoute = { connectionId: 'conn-a', profile: 'writer' }
+    setSessions([{ id: 'listed', title: 'Already listed' } as never])
+    $sessionTiles.set([
+      { ownerRoute, storedSessionId: 'old-chat' },
+      { storedSessionId: 'listed' },
+      { runtimeId: 'rt-live', storedSessionId: 'live' },
+      { storedSessionId: 'bot', workspaceTabTitle: 'Bot Chat' }
+    ])
+
+    const lookup = vi.fn(async (id: string) => {
+      const row = { id, title: 'Quarterly review' } as never
+      setSessions(prev => [row, ...prev])
+
+      return row
+    })
+
+    const stop = startUnrestoredTileTitleBackfill(lookup as never)
+    expect(lookup).not.toHaveBeenCalled()
+
+    $gatewayState.set('open')
+    await vi.waitFor(() => expect(lookup).toHaveBeenCalledTimes(1))
+    expect(lookup).toHaveBeenCalledWith('old-chat', ownerRoute)
+    expect($sessions.get().find(row => row.id === 'old-chat')?.title).toBe('Quarterly review')
+
+    // One-shot: a later reconnect does not re-probe.
+    $gatewayState.set('idle')
+    $gatewayState.set('open')
+    expect(lookup).toHaveBeenCalledTimes(1)
+    stop()
+  })
+})

apps/desktop/src/app/chat/session-tile.tsx

@@ -478,6 +478,33 @@ export function tileStoredRow(storedSessionId: string): SessionInfo | undefined
   )
 }
 
+/** One-shot by-id title fill for restored tiles that never mount (#94167).
+ *  A restored background tab has no runtimeId and does not mount its pane, so
+ *  the resolution effect above never runs; when its row is outside the recents
+ *  page and project tree, `tileTitle()` reads "New session" until first click.
+ *  `resolveStoredSession` upserts the row into `$sessions`, which the tab strip
+ *  already watches — nothing is persisted. Runs once the gateway can answer. */
+export function startUnrestoredTileTitleBackfill(lookup = resolveStoredSession): () => void {
+  const run = () => {
+    if ($gatewayState.get() !== 'open') {
+      return
+    }
+
+    off()
+
+    for (const tile of $sessionTiles.get()) {
+      if (!tile.runtimeId && !tile.workspaceTabTitle && !tileStoredRow(tile.storedSessionId)) {
+        void lookup(tile.storedSessionId, tile.ownerRoute).catch(() => undefined)
+      }
+    }
+  }
+
+  const off = $gatewayState.listen(run)
+  run()
+
+  return off
+}
+
 /** The tab's REGISTERED name. Deliberately the bare placeholder for a draft
  *  rather than its live composer title (`tabTitle` renders that): re-registering
  *  per keystroke would re-render the strip, and holding the draft's text here

apps/desktop/src/app/contrib/controller.tsx

@@ -84,6 +84,7 @@ import { startSessionDrag } from '../chat/session-drag'
 import {
   SessionTileCloseConfirm,
   stackSessionTilesIntoMain,
+  startUnrestoredTileTitleBackfill,
   watchSessionTiles,
   WorkspaceTabMenu
 } from '../chat/session-tile'
@@ -459,6 +460,7 @@ watchContributedPanes()
 // into the transparent overlay).
 if (!isBrowserWindow() && !isHudWindow()) {
   watchSessionTiles()
+  startUnrestoredTileTitleBackfill()
   watchRouteTiles()
   watchPreviewTiles()
 }