fix(deepseek): review-driven hardening across the harness integration

Fifteen review findings on the dsh mode, the serious ones first:

- Multi-user: DEEPSEEK_BASE_URL joins the owner-clamped env keys.
  _configureDeepSeek() forwards the SERVER's own DEEPSEEK_API_KEY into
  every dsh pane and applyEnvOverrides() lands after it, so a non-granted
  owner who could redirect the base URL would have the operator's key sent
  as a bearer credential to a host of their choosing.
- Wait registry: until=stop/blocked is refused on docker and remote-SSH
  dsh sessions (new deepSeekBridgeUnreachable fact in sessionHookOptions).
  The HERDR triple is set via LOCAL tmux setenv, which crosses neither
  docker exec nor ssh, so such a session can never post a hook event and
  the wait burned its whole timeout on every turn.
- Approvals: a dsh item is an ALERT, not an answerable card. The answer
  route refuses (the '1'/Esc keystrokes are Claude-dialog-shaped and the
  option parser cannot read a third-party TUI's frames, so an answer was a
  blind keystroke into a foreign composer), and the push notification
  carries no Approve/Deny actions for dsh sessions.
- Status shim (v3): --seq is forwarded and the server drops stale retried
  reports inside a 60s window (the TUI retries with backoff, so a retried
  'working' could land after 'blocked' and resolve an approval whose
  dialog was still on screen); 4xx responses exit 0 instead of retrying,
  so one misconfigured session cannot feed the auth rate-limit bucket
  until the hook endpoint 429s for the whole instance.
- Web-UI server: concurrent starts are serialized through a lock (two
  racing POSTs used to pick the same port and orphan the winner), and the
  readiness poll / timeout paths only clear or stop the singleton while it
  is still theirs. First click actually opens the tab now
  (refreshWebviews, not the nonexistent loadWebviews). DELETE
  /api/deepseek/web requires the privileged grant in multi-user mode.
- Cron: deepseek jobs run the same two-part launch gate as the HTTP
  create paths (impl moved into the resolver so all three share it) and no
  longer stamp a Claude default model on the session.
- Parity sweeps: quick-start's docker branch rejects deepSeekConfig like
  the remote branch; the Ralph auto-enable list gained deepseek;
  HookEventType gained agent_working; the phone overview run menu filters
  managed webview records like the desktop menu.
- install.sh: the dsh identity probe closes stdin (under curl|bash a
  child that reads stdin eats the rest of the script), bounds the exec
  with timeout where available, and is memoized to one scan per install.
- Welcome screen: .welcome-btn-deepseek styled in the #4d6bfe brand
  identity (it rendered as an unstyled UA-grey button); stale markup
  comment about the web shortcut rewritten; clamp docs updated.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/web/routes/system-routes.ts

@@ -547,7 +547,16 @@ export function registerSystemRoutes(
     return { success: true, data: getDeepSeekWebStatus() };
   });
 
-  app.delete('/api/deepseek/web', async () => {
+  app.delete('/api/deepseek/web', async (req) => {
+    // Same bar as POST: the server is a single shared instance, so in
+    // multi-user mode stopping it out from under other users' tabs is a
+    // privileged act (single-user and granted owners are unaffected).
+    if (isMultiUserMode() && !(await canUsernameRunPrivilegedCommands(getAuthUser(req).username))) {
+      return createErrorResponse(
+        ApiErrorCode.FORBIDDEN,
+        'Stopping the DeepSeek web UI requires the can-bypass-permissions grant'
+      );
+    }
     const { stopDeepSeekWeb } = await import('../../deepseek-web-server.js');
     await stopDeepSeekWeb();
     return { success: true, data: { stopped: true } };