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/subcommands/dashboard.py

@@ -45,26 +45,6 @@ def build_dashboard_parser(
             "where npm may not be available. Pre-build with: cd web && npm run build"
         ),
     )
-    dashboard_parser.add_argument(
-        "--isolated",
-        action="store_true",
-        help=(
-            "When launched from a named profile (e.g. `worker dashboard`), run "
-            "a dedicated dashboard server scoped to that profile instead of "
-            "routing to the machine dashboard. Default behavior is unified: "
-            "profile launches attach to (or start) ONE machine-level dashboard "
-            "and preselect the profile in the UI's profile switcher."
-        ),
-    )
-    # Internal flag set by the unified-launch re-exec (cmd_dashboard) to
-    # preselect the launching profile in the SPA switcher. Hidden from
-    # --help: users get this behavior automatically via `<profile> dashboard`.
-    dashboard_parser.add_argument(
-        "--open-profile",
-        dest="open_profile",
-        default="",
-        help=argparse.SUPPRESS,
-    )
     # Lifecycle flags — mutually exclusive with each other and with the
     # start-a-server flags above (if both are passed, --stop / --status win
     # because they exit before the server is started).  The dashboard has