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>

test/render-index-html.test.ts

@@ -19,6 +19,7 @@ import { isGeminiAvailable } from '../src/utils/gemini-cli-resolver.js';
 import { isAntigravityAvailable } from '../src/utils/antigravity-cli-resolver.js';
 import { isPiAvailable } from '../src/utils/pi-cli-resolver.js';
 import { isGrokAvailable } from '../src/utils/grok-cli-resolver.js';
+import { isDeepSeekAvailable, isDeepSeekRunnable } from '../src/utils/deepseek-cli-resolver.js';
 import { isCloudflaredAvailable } from '../src/utils/cloudflared-resolver.js';
 import { isGitAvailable } from '../src/git-clone.js';
 
@@ -55,6 +56,16 @@ vi.mock('../src/utils/grok-cli-resolver.js', () => ({
   resolveGrokDir: vi.fn(() => null),
   getGrokCliVersion: vi.fn(() => null),
 }));
+// DeepSeek is the one mode with a two-part availability answer (binary AND a
+// pane-capable profile), so both probes are mocked independently.
+vi.mock('../src/utils/deepseek-cli-resolver.js', () => ({
+  isDeepSeekAvailable: vi.fn(() => false),
+  isDeepSeekRunnable: vi.fn(() => false),
+  resolveDeepSeekDir: vi.fn(() => null),
+  getDeepSeekCliVersion: vi.fn(() => null),
+  listDeepSeekProfiles: vi.fn(() => []),
+  resolveDefaultDeepSeekProfile: vi.fn(() => null),
+}));
 vi.mock('../src/utils/cloudflared-resolver.js', () => ({
   isCloudflaredAvailable: vi.fn(() => false),
   resolveCloudflaredPath: vi.fn(() => null),
@@ -160,6 +171,8 @@ describe('WebServer.renderIndexHtml', () => {
       antigravity: false,
       pi: true,
       grok: false,
+      deepseek: false,
+      deepseekBinary: false,
       cloudflared: true,
       git: true,
     });
@@ -176,6 +189,8 @@ describe('WebServer.renderIndexHtml', () => {
       isAntigravityAvailable,
       isPiAvailable,
       isGrokAvailable,
+      isDeepSeekAvailable,
+      isDeepSeekRunnable,
       isCloudflaredAvailable,
       isGitAvailable,
     ]) {