fix(desktop): keep a window-state IPC that lands before the first connection publishes

`onWindowStateChanged` merged the fullscreen / traffic-light payload into
`$connection`, but only when a connection was already published; while
`$connection` was null (mid-boot, or between a dropped primary and its
fallback resolving) the payload was dropped. Main snapshots the chrome
state into each descriptor at mint time, so a toggle that fires after the
mint but before the renderer publishes it is newer than the snapshot and
never reached the titlebar cluster until the next toggle — the third
root-cause atom of #108641.

Buffer the last payload while nothing is published and fold it into the
next non-null publish, then clear it: later descriptors carry their own
fresh snapshot.

apps/desktop/src/app/gateway/hooks/use-gateway-boot.test.tsx

@@ -2248,3 +2248,40 @@ describe('useGatewayBoot remote reconnect loop (real hook, fake socket)', () =>
     expect($gatewayState.get()).toBe('open')
   })
 })
+
+describe('window-state IPC before the first connection publishes (#108641)', () => {
+  it('a fullscreen toggle that lands while getConnection is still pending reaches the published connection', async () => {
+    // Main snapshots chrome state into the descriptor at mint time; a toggle
+    // that fires after the mint but before the renderer publishes it is newer
+    // than the snapshot and used to be dropped because $connection was null.
+    let windowState: ((payload: Record<string, unknown>) => void) | null = null
+    const pending = deferred<Record<string, unknown>>()
+
+    const desktop = {
+      ...fakeDesktop(),
+      getConnection: vi.fn(() => pending.promise),
+      onWindowStateChanged: vi.fn((callback: (payload: Record<string, unknown>) => void) => {
+        windowState = callback
+
+        return () => undefined
+      })
+    }
+
+    ;(window as { hermesDesktop?: unknown }).hermesDesktop = desktop
+
+    render(<Harness />)
+    await flushAsync()
+    expect($connection.get()).toBeNull()
+
+    act(() => windowState?.({ isFullscreen: true, nativeOverlayWidth: 0, windowButtonPosition: null }))
+    expect($connection.get()).toBeNull()
+
+    await act(async () => {
+      pending.resolve({ ...primaryConn, isFullscreen: false, windowButtonPosition: { x: 12, y: 16 } })
+      await vi.advanceTimersByTimeAsync(0)
+    })
+
+    expect($connection.get()?.isFullscreen).toBe(true)
+    expect($connection.get()?.windowButtonPosition).toBeNull()
+  })
+})

apps/desktop/src/app/gateway/hooks/use-gateway-boot.ts

@@ -10,7 +10,7 @@ import {
 import { useEffect, useRef } from 'react'
 
 import { shouldApplyPostBootProgressError } from '@/components/boot-failure-reauth'
-import type { DesktopBootProgress, HermesConnection } from '@/global'
+import type { DesktopBootProgress, HermesConnection, HermesWindowState } from '@/global'
 import { HermesGateway } from '@/hermes'
 import { translateNow } from '@/i18n'
 import { desktopDefaultCwd } from '@/lib/desktop-fs'
@@ -199,7 +199,20 @@ export function useGatewayBoot({
     let cancelled = false
     const desktop = window.hermesDesktop
 
+    // Window-state IPC (fullscreen / traffic-light position) that lands while
+    // no connection is published — mid-boot, or between a dropped primary and
+    // its fallback resolving — has nowhere to merge into. Main snapshots the
+    // chrome state into each descriptor at mint time, so a toggle that happens
+    // AFTER the mint but BEFORE the renderer publishes it is newer than the
+    // snapshot and would otherwise be lost until the next toggle (#108641).
+    let pendingWindowState: HermesWindowState | null = null
+
     const publish = (next: HermesConnection | null) => {
+      if (next && pendingWindowState) {
+        next = { ...next, ...pendingWindowState }
+        pendingWindowState = null
+      }
+
       callbacksRef.current.onConnectionReady(next)
       setConnection(next)
       desktop?.setActiveConnectionRoute?.(
@@ -1108,6 +1121,8 @@ export function useGatewayBoot({
 
       if (current) {
         publish({ ...current, ...payload })
+      } else {
+        pendingWindowState = payload
       }
     })