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

internal/federation/federation_test.go

@@ -75,3 +75,33 @@ func TestOfflineHookRunsOnceOnTransition(t *testing.T) {
 	case <-time.After(10 * time.Millisecond):
 	}
 }
+
+func TestCaptureRevisionAndCommandQueue(t *testing.T) {
+	r := &Registry{}
+	if err := r.Register(Worker{ID: "w", Token: "t"}, ""); err != nil {
+		t.Fatal(err)
+	}
+	c, err := r.PutCapture("w", Capture{TaskID: "task", PaneID: "pane", Text: "Permission required\n$ ls"})
+	if err != nil || c.Revision != 1 {
+		t.Fatalf("capture=%#v err=%v", c, err)
+	}
+	again, err := r.PutCapture("w", Capture{TaskID: "task", PaneID: "pane", Text: c.Text})
+	if err != nil || again.Revision != 1 {
+		t.Fatalf("same capture=%#v err=%v", again, err)
+	}
+	cmd, err := r.Queue("w", Command{TaskID: "task", Kind: "grant_approval", PaneID: "pane", CaptureRevision: 1})
+	if err != nil {
+		t.Fatal(err)
+	}
+	commands, err := r.Commands("w")
+	if err != nil || len(commands) != 1 || commands[0].ID != cmd.ID {
+		t.Fatalf("commands=%#v err=%v", commands, err)
+	}
+	if err := r.CompleteCommand("w", cmd.ID, "acknowledged", ""); err != nil {
+		t.Fatal(err)
+	}
+	commands, _ = r.Commands("w")
+	if len(commands) != 0 {
+		t.Fatalf("pending=%#v", commands)
+	}
+}