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.

hermes_cli/dump.py

@@ -318,17 +318,6 @@ def run_dump(args):
             display = _redact(val)
         else:
             display = "set" if val else "not set"
-        # A credential added via `hermes auth add openrouter` lives in the
-        # credential pool, not as an env var — surface it so the dump doesn't
-        # misleadingly read "not set" while `hermes auth list` shows it (#42130).
-        if not val and label == "openrouter":
-            try:
-                from agent.credential_pool import load_pool as _load_pool
-
-                if _load_pool("openrouter").has_credentials():
-                    display = "set (auth pool)"
-            except Exception:
-                pass
         lines.append(f"  {label:<20} {display}")
 
     # Features summary