Add web UI and worker capture/approval command channel

Introduces the browser-facing surface and the worker-side protocol that
backs it:

- internal/ui: joined read model plus per-task lifecycle and approval
  controls, kept separate from the raw endpoints workers and harnesses
  depend on.
- internal/webui + web/: Vite/React app, build output embedded via
  go:embed and served as an SPA fallback.
- federation: per-(worker, task) captures with a monotonic revision that
  advances only when pane text actually changes, and a command queue
  restricted to grant_approval / deny_approval, each bound to the capture
  revision the operator acted on.
- orchestra-worker: publishes captures and executes commands only after
  re-reading the pane and confirming the revision still matches. Sends
  keystrokes only for a visible y/n prompt or OpenCode's fully labelled
  selector, and refuses to deny through that selector rather than guess
  at unobservable navigation.

This is the ownership boundary AUDIT.md's B14 and B17 call for: approval
becomes an explicit, revision-bound operation executed by the worker that
owns the pane, instead of a side effect of prompting over a
coordinator-driven remote socket.

Also ignores the web build inputs and outputs. node_modules ships vendored
Go packages, so go build and go test walk into it if it is merely
untracked; both node_modules and .node_modules are excluded.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01535A3Y8RtkAi8wYuWhtkEd

web/src/api/client.test.ts

@@ -0,0 +1,19 @@
+import {afterEach,describe,expect,it,vi} from 'vitest'
+import {api} from './client'
+
+describe('UI API client',()=>{
+  afterEach(()=>vi.unstubAllGlobals())
+  it('submits every supplied task field to the UI creation endpoint',async()=>{
+    const fetch=vi.fn().mockResolvedValue(new Response(JSON.stringify({task_id:'t'}),{status:200}))
+    vi.stubGlobal('fetch',fetch)
+    await api.create({source:'web',external_id:'x',project:'p',parent:'parent',inherent_priority:2})
+    expect(fetch).toHaveBeenCalledWith('/v1/ui/tasks',expect.objectContaining({method:'POST'}))
+    expect((fetch.mock.calls[0][1].body as string)).toContain('"parent":"parent"')
+  })
+  it('uploads a completion report before a task completion action',async()=>{
+    const fetch=vi.fn().mockResolvedValue(new Response(JSON.stringify({ref:'a'.repeat(64)}),{status:201}))
+    vi.stubGlobal('fetch',fetch)
+    await expect(api.upload('report')).resolves.toBe('a'.repeat(64))
+    expect(fetch).toHaveBeenCalledWith('/v1/artifacts',expect.objectContaining({method:'POST',body:'report'}))
+  })
+})