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.

plugins/google_meet/audio_bridge.py

@@ -86,7 +86,6 @@ class AudioBridge:
                         ["pactl", "unload-module", str(mod_id)],
                         check=False,
                         capture_output=True,
-                        stdin=subprocess.DEVNULL,
                     )
                 except Exception:
                     # Best-effort teardown — never raise from here.
@@ -112,7 +111,6 @@ class AudioBridge:
                 check=True,
                 capture_output=True,
                 text=True,
-                stdin=subprocess.DEVNULL,
             )
         except FileNotFoundError as exc:
             raise RuntimeError(
@@ -137,7 +135,6 @@ class AudioBridge:
                 check=True,
                 capture_output=True,
                 text=True,
-                stdin=subprocess.DEVNULL,
             )
         except subprocess.CalledProcessError as exc:
             # Roll back the null-sink we just created so we don't leak it.
@@ -145,7 +142,6 @@ class AudioBridge:
                 ["pactl", "unload-module", str(sink_mod_id)],
                 check=False,
                 capture_output=True,
-                stdin=subprocess.DEVNULL,
             )
             raise RuntimeError(
                 f"pactl load-module virtual-source failed: {exc.stderr or exc}"