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.

tests/cron/test_parallel_pool.py

@@ -172,10 +172,10 @@ class TestSyncMode:
 
 
 class TestSequentialPool:
-    """Sequential (workdir) jobs use the persistent cron-seq pool.
+    """Sequential (workdir/profile) jobs use the persistent cron-seq pool.
 
-    Verifies the follow-up fix: env-mutating jobs no longer run inline
-    in the ticker thread, so a long workdir job can't starve the
+    Verifies the follow-up fix: env/context-mutating jobs no longer run inline
+    in the ticker thread, so a long workdir/profile job can't starve the
     schedule the same way the parallel path used to.
     """