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>

skills/codeman/reference/messaging.md

@@ -56,7 +56,7 @@ own head: the worker enforcing the cap is the one who has to be told about it.
 | synchronize on end of turn | HTTP `wait until=stop` (fires for message-initiated turns too, verified live) |
 | liveness / death check | HTTP `wait?until=exit` |
 | interrupt a running turn (break-glass) | HTTP input, a bare `\x1b` with no `\r` |
-| non-claude modes (`shell`/`opencode`/`codex`/`gemini`/`antigravity`/`pi`/`grok`) | HTTP only (no other CLI has messaging) |
+| non-claude modes (`shell`/`opencode`/`codex`/`gemini`/`antigravity`/`pi`/`grok`/`deepseek`) | HTTP only (no other CLI has messaging) |
 | delete | HTTP, via SKILL.md's `delete_session` guard |
 
 ## Availability: probe, never assume
@@ -347,7 +347,7 @@ Without a break-glass, a pair with a bad brief is a token bonfire with no off sw
 
 ### Mixed fleets: the pairing matrix
 
-Non-claude workers (`shell`, `opencode`, `codex`, `gemini`, `antigravity`, `pi`, `grok`) cannot be peers
+Non-claude workers (`shell`, `opencode`, `codex`, `gemini`, `antigravity`, `pi`, `grok`, `deepseek`) cannot be peers
 at all; no other CLI has this feature. Their tasks route over HTTP, and you never mention
 messaging in their briefs. The claude half of the fleet can use messaging among itself,
 subject to the namespace rule: **messaging works between two sessions that share one