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/public/styles.css

@@ -3892,6 +3892,24 @@ body.touch-device .terminal-container .xterm .xterm-helper-textarea {
   transform: translateY(-1px);
 }
 
+/* DeepSeek Harness: the #4d6bfe blue identity, matching
+   .btn-toolbar.btn-run.mode-deepseek and .run-mode-dot.deepseek so the welcome
+   action reads as the same backend. */
+.welcome-btn-deepseek {
+  background: linear-gradient(135deg, #101a4d 0%, #2740c4 55%, #4d6bfe 100%);
+  border-color: rgba(124, 147, 255, 0.4);
+  color: #eef2ff;
+  box-shadow: 0 2px 8px rgba(77, 107, 254, 0.16), inset 0 1px 0 rgba(255, 255, 255, 0.06);
+}
+
+.welcome-btn-deepseek:hover {
+  background: linear-gradient(135deg, #16225f 0%, #3350e6 55%, #6b83ff 100%);
+  box-shadow: 0 4px 20px rgba(77, 107, 254, 0.3), 0 0 40px rgba(39, 64, 196, 0.12), inset 0 1px 0 rgba(255, 255, 255, 0.08);
+  border-color: rgba(150, 170, 255, 0.5);
+  color: #f8faff;
+  transform: translateY(-1px);
+}
+
 .welcome-btn-gemini {
   background: linear-gradient(135deg, #10243f 0%, #174ea6 55%, #4f46e5 100%);
   border-color: rgba(96, 165, 250, 0.4);