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/__init__.py

@@ -19,74 +19,29 @@ __release_date__ = "2026.6.5"
 
 
 def _ensure_utf8():
-    """Force UTF-8 stdout/stderr to prevent UnicodeEncodeError crashes.
+    """Force UTF-8 stdout/stderr on Windows to prevent UnicodeEncodeError.
 
-    Several environments select a legacy, non-UTF-8 encoding for the standard
-    streams:
-
-    - Windows services and terminals default to cp1252.
-    - Linux hosts with a latin-1 / C / POSIX locale (common on minimal Debian
-      installs and Raspberry Pi) select latin-1 or ASCII.
-
-    The CLI prints box-drawing characters (┌│├└─) and the ⚕ glyph in the setup
-    wizard, doctor, and status banners. Encoding those under a non-UTF-8 codec
-    raises an unhandled UnicodeEncodeError that crashes the command before it
-    can even start — e.g. `hermes setup` on a fresh Pi.
-
-    This runs at import time so it protects every CLI subcommand, on any
-    platform. It re-wraps stdout/stderr as UTF-8 when their encoding is not
-    already UTF-8, preferring TextIOWrapper.reconfigure() so the existing
-    stream object is fixed in place (cached `sys.stdout` references keep
-    working) and falling back to reopening the file descriptor with
-    closefd=False (the CPython-recommended safe variant).
-
-    No-op when the streams are already UTF-8: a healthy UTF-8 system sees no
-    stream change and no environment mutation.
-
-    Note: this is intentionally the earliest, platform-agnostic guard.
-    hermes_cli/stdio.py::configure_windows_stdio() runs later from the entry
-    points and layers on the Windows-only extras (console code-page flip,
-    EDITOR default, PATH augmentation); its stream reconfiguration is a
-    harmless idempotent no-op once we have already repaired the streams here.
+    Windows services and terminals default to cp1252, which cannot encode
+    box-drawing characters used in CLI output. This causes unhandled
+    UnicodeEncodeError crashes on gateway startup.
     """
-    repaired = False
-
+    if sys.platform != "win32":
+        return
+    os.environ.setdefault("PYTHONUTF8", "1")
+    os.environ.setdefault("PYTHONIOENCODING", "utf-8")
     for stream_name in ("stdout", "stderr"):
         stream = getattr(sys, stream_name, None)
         if stream is None:
             continue
         try:
-            encoding = (getattr(stream, "encoding", "") or "").lower().replace("-", "")
-            if encoding == "utf8":
-                continue
-
-            # Preferred: reconfigure the existing TextIOWrapper in place. This
-            # preserves object identity so any code already holding a reference
-            # to the old sys.stdout benefits from the repair too.
-            reconfigure = getattr(stream, "reconfigure", None)
-            if callable(reconfigure):
-                reconfigure(encoding="utf-8", errors="replace")
-                repaired = True
-                continue
-
-            # Fallback: reopen the underlying file descriptor as UTF-8. Used
-            # for streams that don't expose reconfigure() (e.g. some wrapped
-            # or replaced streams). closefd=False keeps the original fd open.
-            new_stream = open(
-                stream.fileno(), "w", encoding="utf-8",
-                errors="replace", buffering=1, closefd=False,
-            )
-            setattr(sys, stream_name, new_stream)
-            repaired = True
-        except (AttributeError, OSError, ValueError):
+            if getattr(stream, "encoding", "").lower().replace("-", "") != "utf8":
+                new_stream = open(
+                    stream.fileno(), "w", encoding="utf-8",
+                    buffering=1, closefd=False,
+                )
+                setattr(sys, stream_name, new_stream)
+        except (AttributeError, OSError):
             pass
 
-    # Only nudge child processes toward UTF-8 when we actually detected a
-    # non-UTF-8 locale. On a healthy UTF-8 host children inherit UTF-8 from the
-    # locale already, so leave the environment untouched (minimal footprint).
-    if repaired:
-        os.environ.setdefault("PYTHONUTF8", "1")
-        os.environ.setdefault("PYTHONIOENCODING", "utf-8")
-
 
 _ensure_utf8()