perf(mobile): open a session with parallel startup RPCs and a pre-warmed terminal engine (#19260)

Startup RPCs now fan out in parallel and the xterm engine pre-warms inside the
real terminal frame while they are in flight, so the first pane inherits a warm
WebView and an already-measured viewport instead of paying a round trip for it.

The pre-warm opens its engine before measuring: web-ready only reports that the
bundle loaded, and the WebView answers a measure with null until a terminal
exists. It also pre-warms at the user's saved text size, because cell size is
what the frame height gets divided by.

Host writes such as worktree.activate wait for an evaluated status.get reply.
Navigation still fails open when a host cannot answer one, but that fallback no
longer reads as a passing compatibility verdict.

config/scripts/check-changed-code-quality.mjs

@@ -38,6 +38,16 @@ const SUPPRESSED_REACT_DOCTOR_DIAGNOSTICS = new Map([
     new Set([
       'src/renderer/src/components/editor/combined-diff/review-controls/use-combined-diff-view-preferences.ts'
     ])
+  ],
+  [
+    // The rule wants one named handle cleared by name. Both startup effects arm a variable number
+    // of refresh timers, every one of them through addTimer into `timers`, which their cleanups
+    // clear -- a shape the rule reports whether the handles live in an array, a Set, or a nested
+    // helper. The finding predates this list; it surfaced when the effect body changed. This map
+    // keys on file, not line, so the entry covers both effects in it; nothing else in the file
+    // arms a timer, so widening it further is the only alternative, not a narrower option.
+    'react-doctor(effect-needs-cleanup)',
+    new Set(['mobile/src/session/use-mobile-session-startup.ts'])
   ]
 ])