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.

website/docs/user-guide/profiles.md

@@ -199,20 +199,6 @@ If you want this profile to work in a specific project by default, also set its
 coder config set terminal.cwd /absolute/path/to/project
 ```
 
-### From the dashboard
-
-The [web dashboard](features/web-dashboard.md#managing-multiple-profiles)
-is a machine-level surface that can manage **any** profile's config, API
-keys, skills, MCPs, and model via the profile switcher in its sidebar — no
-per-profile dashboard needed. `coder dashboard` routes to the machine
-dashboard with the `coder` profile preselected. The dashboard's Chat tab
-also follows the switcher, spawning a conversation under the selected
-profile's home.
-
-Note: "Set as active" on the dashboard's Profiles page is the sticky
-default for **future CLI/gateway runs** (same as `hermes profile use`) —
-to edit a profile from the dashboard, use the switcher instead.
-
 ## Updating
 
 `hermes update` pulls code once (shared) and syncs new bundled skills to **all** profiles automatically: