feat(deepseek): add DeepSeek Harness (dsh) as a ninth CLI run mode

Adds `mode: 'deepseek'` alongside claude/shell/opencode/codex/gemini/
antigravity/pi/grok, plus a shortcut that opens the harness's own browser UI
as a Codeman web tab.

DeepSeek is wired unlike its siblings in three ways, each of which is the
reason for a design decision rather than an accident:

1. The agent is a PROFILE, not the binary. `dsh` is a launcher over
   $DSH_HOME/profiles/<name>, and DeepSeek ships only `web`, `headless` and
   `base` -- the interactive terminal front door is always a third-party
   plugin. So availability is two questions: `isDeepSeekAvailable()` (binary)
   and `isDeepSeekRunnable()` (binary AND a pane-capable profile). The Run
   button gates on the latter, because reporting only the binary would spawn a
   pane that dies on arrival. When the binary is present but no profile is,
   the run menu offers to install one (POST /api/deepseek/install-profile).

2. The permission switch is an env var, not a flag. The harness has no
   command-line permission option; its sandbox/approval rows read
   DSH_PERMISSION_MODE (read-only / workspace-write / danger-full-access).
   Exported via `tmux setenv`, never on the spawn line. Absent = the harness's
   own workspace-write, which still asks, so the multi-user clamp is the
   only-if-sent branch and clamps to workspace-write, never read-only.

3. It is the only non-claude mode that passes hooksAvailableForMode(), and it
   earned that. The terminal front door reports idle/working/blocked to a
   supervising process over a generic env-gated contract; a generated shim
   (deepseek-status-shim.ts) makes Codeman that supervisor and forwards each
   report to /api/hook-event as stop / agent_working / permission_prompt. So a
   dsh session gets definitive respawn triggers, real wait-endpoint signals and
   real Approvals Inbox items instead of output-stabilization guesswork.
   `agent_working` is new (157th SSE constant) and joins
   APPROVAL_RESOLVING_EVENTS so a dialog answered in the terminal clears its
   alert at once.

The resolver needs the strictest identity probe of the family: `dsh` is not
merely a squattable npm name, Debian ships an unrelated `dsh` (dancer's shell),
so `dsh --help` must print the harness's own banner before a candidate is
handed a spawn line.

Model is deliberately not a session field -- it is a composition entry in the
profile's config tree. Env allowlist gains DSH_* and DEEPSEEK_* only; provider
keys named by a settings-file `apiKeyEnv` stay out, which is pi's
34-provider-key problem in a new shape.

Verified live against dsh 0.1.1-rc.2 and @deepseek-harness-tui/dsh-tui: the
status endpoint's two-part answer, the no-profile refusal, the profile
bootstrap, a real session whose pane runs `dsh --profile dsh-tui` with the
permission mode injected via setenv, and the full status bridge -- a
send-and-wait returned signal "stop" from a real turn, and blocked/working
created and cleared an Approvals Inbox item.

Docs: docs/deepseek-integration.md (guide), docs/deepseek-integration-plan.md
(decisions + honest gaps). Tests: test/deepseek-mode.test.ts,
test/deepseek-cli-resolver.test.ts.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/web/sse-events.ts

@@ -5,7 +5,7 @@
  * and referenced by the frontend (`SSE_EVENTS` in `constants.js`).
  * Both files MUST be kept in sync.
  *
- * 156 event constants organized by category:
+ * 157 event constants organized by category:
  * - **Core** (1): init
  * - **Transport** (1): sse:heartbeat
  * - **Session lifecycle** (23): created, updated, deleted, terminal, idle, working, ...
@@ -25,7 +25,8 @@
  * - **Plan orchestration** (5): started, progress, subagent, completed, cancelled
  * - **Tunnel** (7): started, stopped, progress, error, qrRotated, qrRegenerated, qrAuthUsed
  * - **Image / attachments** (2): image:detected, attachment:detected
- * - **Hooks** (8): idle_prompt, permission_prompt, elicitation_dialog, elicitation_complete, elicitation_response, stop, teammate_idle, task_completed
+ * - **Hooks** (9): idle_prompt, permission_prompt, elicitation_dialog, elicitation_complete, elicitation_response, stop, agent_working, teammate_idle, task_completed
+ *   (agent_working is the odd one out: reported by the DeepSeek Harness status bridge, not by a Claude Code hook)
  * - **Approvals** (3): pending, updated, resolved (cross-session Approvals Inbox)
  * - **Orchestrator** (12): stateChanged, planProgress, planReady, phase*, verification, task*, completed, error
  * - **Clipboard** (1): write
@@ -360,6 +361,13 @@ export const HookElicitationComplete = 'hook:elicitation_complete' as const;
 export const HookElicitationResponse = 'hook:elicitation_response' as const;
 /** Claude Code hook: response complete. */
 export const HookStop = 'hook:stop' as const;
+/**
+ * Agent started a turn. NOT a Claude Code hook: this one is reported by the
+ * DeepSeek Harness status bridge, which is why the name is agent-generic. It
+ * exists so a dialog answered in the terminal clears its alert immediately
+ * instead of waiting for the turn to end.
+ */
+export const HookAgentWorking = 'hook:agent_working' as const;
 /** Claude Code hook: teammate went idle. */
 export const HookTeammateIdle = 'hook:teammate_idle' as const;
 /** Claude Code hook: teammate task completed. */
@@ -619,6 +627,7 @@ export const SseEvent = {
   HookElicitationComplete,
   HookElicitationResponse,
   HookStop,
+  HookAgentWorking,
   HookTeammateIdle,
   HookTaskCompleted,