feat(dashboard): always enable embedded chat; remove dashboard --tui flag

The dashboard's embedded Chat surface (/chat, /api/ws, /api/pty) was gated
behind `hermes dashboard --tui` / HERMES_DASHBOARD_TUI=1. The desktop app and
the dashboard's own Chat tab both drive the agent over the /api/ws + /api/pty
WebSockets, so a dashboard started without the flag would pass the /api/status
health check but slam the chat WebSocket shut with WS code 4403 — the app
connects, reports "ready", and chat stays dead. This was the root cause behind
multiple user reports of the desktop app failing to connect to a self-hosted
gateway/dashboard, and it bit Docker and host installs alike.

Make the embedded chat unconditional:

- web_server.py: _DASHBOARD_EMBEDDED_CHAT_ENABLED defaults to True; drop the
  embedded_chat parameter and the runtime reassignment from start_server().
  The WS gates still read the constant (now always true) so the seam — and its
  "rejects when disabled" contract test — stays meaningful.
- main.py: remove the `--tui` argument from the dashboard subparser and the
  `embedded_chat = args.tui or HERMES_DASHBOARD_TUI==1` derivation.
- web/: isDashboardEmbeddedChatEnabled() returns true unconditionally; drop the
  deprecated __HERMES_DASHBOARD_TUI__ alias and the dead LEGACY_TUI_RE scrape in
  the vite dev-token plugin.
- apps/desktop/electron/main.cjs: drop `--tui` from the spawned dashboardArgs
  (it would now error with "unrecognized arguments: --tui") and the redundant
  HERMES_DASHBOARD_TUI env injection.
- Docker: no s6 run-script change needed — the script never passed --tui; the
  HERMES_DASHBOARD_TUI env var is now simply a no-op, so the image works out of
  the box with no extra var.
- Docs: remove every dashboard --tui / HERMES_DASHBOARD_TUI reference across the
  CLI reference, env-var reference, docker/desktop/web-dashboard guides, in-app
  tips, and the zh-Hans translations. The terminal `hermes --tui` / HERMES_TUI
  references are intentionally left untouched.

Tests: 270 passing across web_server, dashboard lifecycle, host-header,
auth-gate, and docker-override-scripts suites.

website/docs/reference/cli-commands.md

@@ -1342,14 +1342,13 @@ hermes claw migrate --source /home/user/old-openclaw
 hermes dashboard [options]
 ```
 
-Launch the web dashboard — a browser-based UI for managing configuration, API keys, and monitoring sessions. Requires `pip install hermes-agent[web]` (FastAPI + Uvicorn). The embedded browser Chat tab requires `--tui` plus the `pty` extra. See [Web Dashboard](/user-guide/features/web-dashboard) for full documentation.
+Launch the web dashboard — a browser-based UI for managing configuration, API keys, and monitoring sessions. Requires `pip install hermes-agent[web]` (FastAPI + Uvicorn). The embedded browser Chat tab is always available and additionally needs the `pty` extra (`pip install 'hermes-agent[web,pty]'`) plus a POSIX PTY environment such as Linux, macOS, or WSL2. See [Web Dashboard](/user-guide/features/web-dashboard) for full documentation.
 
 | Option | Default | Description |
 |--------|---------|-------------|
 | `--port` | `9119` | Port to run the web server on |
 | `--host` | `127.0.0.1` | Bind address |
 | `--no-open` | — | Don't auto-open the browser |
-| `--tui` | off | Enable the in-browser Chat tab by running `hermes --tui` behind a PTY/WebSocket bridge. Requires `pip install 'hermes-agent[web,pty]'` and a POSIX PTY environment such as Linux, macOS, or WSL2. |
 | `--insecure` | off | Allow binding to non-localhost hosts. Exposes dashboard credentials on the network; use only behind trusted network controls. |
 | `--stop` | — | Stop running `hermes dashboard` processes and exit. |
 | `--status` | — | List running `hermes dashboard` processes and exit. |
@@ -1360,9 +1359,6 @@ hermes dashboard
 
 # Custom port, no browser
 hermes dashboard --port 8080 --no-open
-
-# Enable the browser Chat tab
-hermes dashboard --tui
 ```
 
 ## `hermes profile`