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/memory/hindsight/__init__.py

@@ -695,7 +695,6 @@ class HindsightMemoryProvider(MemoryProvider):
                 subprocess.run(
                     [uv_path, "pip", "install", "--python", sys.executable, "--quiet", "--upgrade"] + deps_to_install,
                     check=True, timeout=120, capture_output=True,
-                    stdin=subprocess.DEVNULL,
                 )
                 print("  ✓ Dependencies up to date")
             except Exception as e:
@@ -1102,7 +1101,6 @@ class HindsightMemoryProvider(MemoryProvider):
                             [uv_path, "pip", "install", "--python", sys.executable,
                              "--quiet", "--upgrade", f"hindsight-client>={_MIN_CLIENT_VERSION}"],
                             check=True, timeout=120, capture_output=True,
-                            stdin=subprocess.DEVNULL,
                         )
                         logger.info("hindsight-client upgraded to >=%s", _MIN_CLIENT_VERSION)
                     except Exception as e: