opentui(phase3): launcher integration — HERMES_TUI_ENGINE dual-engine

hermes --tui launches the native OpenTUI engine (Bun) when
HERMES_TUI_ENGINE=opentui (env) or display.tui_engine=opentui (config);
Ink stays the default and the shipping path is untouched.

- _resolve_tui_engine() (env > config > ink); refuses opentui on
  Windows/Termux (no Bun) -> falls back to ink with a notice.
- _make_opentui_argv() -> [bun, src/entry.real.tsx] (no build step).
- _bun_bin() with HERMES_BUN override.
- Branch at top of _make_tui_argv BEFORE _ensure_tui_node (Bun-only host
  must not bootstrap Node).
- Gate _launch_tui NODE_OPTIONS/--max-old-space-size on engine==ink (Bun
  is JSC; the V8 flag errors/ignores).

Verified end-to-end via tmux: real hermes --tui -> Bun -> OpenTUI ->
real Python gateway streamed a real reply. No-flag default still ink.

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

@@ -3,7 +3,6 @@ import { useEffect, useRef } from 'react'
 import type { HermesConnection } from '@/global'
 import { HermesGateway } from '@/hermes'
 import { translateNow } from '@/i18n'
-import { desktopDefaultCwd } from '@/lib/desktop-fs'
 import { isGatewayReauthRequired, resolveGatewayWsUrl } from '@/lib/gateway-ws-url'
 import {
   $desktopBoot,
@@ -26,16 +25,11 @@ import {
 import { notify, notifyError } from '@/store/notifications'
 import { $activeGatewayProfile, normalizeProfileKey, touchActiveGatewayBackend } from '@/store/profile'
 import {
-  $activeSessionId,
   $attentionSessionIds,
   $connection,
-  $currentCwd,
   $sessions,
   $workingSessionIds,
-  ensureDefaultWorkspaceCwd,
   setConnection,
-  setCurrentBranch,
-  setCurrentCwd,
   setSessionsLoading
 } from '@/store/session'
 import type { RpcEvent } from '@/types/hermes'
@@ -357,12 +351,6 @@ export function useGatewayBoot({
           message: translateNow('boot.steps.loadingSettings'),
           progress: 97
         })
-        await ensureDefaultWorkspaceCwd()
-        const remoteDefault = await desktopDefaultCwd().catch(() => null)
-        if (remoteDefault?.cwd && !$activeSessionId.get() && !$currentCwd.get()) {
-          setCurrentCwd(remoteDefault.cwd)
-          setCurrentBranch(remoteDefault.branch || '')
-        }
         await callbacksRef.current.refreshHermesConfig()
 
         if (cancelled) {