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/client.go

@@ -181,3 +181,31 @@ func (c Client) Complete(ctx context.Context, taskID, reportRef string) error {
 	}
 	return err
 }
+
+func (c Client) PublishCapture(ctx context.Context, capture Capture) (Capture, error) {
+	resp, err := c.request(ctx, http.MethodPost, "/v1/federation/workers/"+url.PathEscape(c.WorkerID)+"/captures", capture)
+	if err != nil {
+		return Capture{}, err
+	}
+	defer resp.Body.Close()
+	var out Capture
+	err = json.NewDecoder(resp.Body).Decode(&out)
+	return out, err
+}
+func (c Client) Commands(ctx context.Context) ([]Command, error) {
+	resp, err := c.request(ctx, http.MethodGet, "/v1/federation/commands", nil)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+	var out []Command
+	err = json.NewDecoder(resp.Body).Decode(&out)
+	return out, err
+}
+func (c Client) ResolveCommand(ctx context.Context, id, status, message string) error {
+	resp, err := c.request(ctx, http.MethodPost, "/v1/federation/commands/"+url.PathEscape(id), map[string]string{"status": status, "message": message})
+	if resp != nil {
+		resp.Body.Close()
+	}
+	return err
+}