Add document-review UIWorker example

Synthesis example: a ReplyToolMixin UIWorker adds a start_review tool that fans
out to clarity/tone peers via start_user_job_group, translates each reviewer
response into an add_note command in on_job_response, handles a client
note_click event via @on_ui_event, and keeps history across turns.

examples/multi-worker/ui-worker/document-review/README.md

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+# document-review
+
+The synthesis demo. A voice-driven workspace where the user reviews a
+draft article — combining the patterns from every prior demo into one
+application: snapshot reading, deixis (read + write), form-fill
+state-changing actions, async job-group fan-out with progress streaming,
+plus one custom command and one client-emitted event.
+
+## What it shows
+
+- **Read-side deixis**: select a paragraph, ask "review this", and the
+  worker grounds in the selected text.
+- **Async fan-out**: a paragraph review spawns two peer workers (clarity
+  + tone) in parallel via `start_user_job_group`. The in-flight card
+  streams each worker's progress.
+- **Custom UI command**: as each worker completes, `on_job_response`
+  emits an `add_note` command with the worker's feedback; the client
+  renders a note attached to the reviewed paragraph.
+- **State-changing actions**: dictating a note fills the textarea and
+  clicks Save (`fills` + `click` from the bundled `reply` tool).
+- **Write-side deixis**: "where does it talk about rhythms?" → the worker
+  finds the paragraph and uses `select_text` to put the page selection
+  on it.
+- **Client-emitted UI event**: clicking a note sends a `note_click` event
+  back; the worker's `@on_ui_event("note_click")` handler dispatches
+  `select_text` to jump to the paragraph. The round-trip event/command
+  pattern.
+- **Two LLM tools coexisting**: `ReplyToolMixin`'s `reply` handles normal
+  turns; a custom `start_review` tool handles review kick-off. The prompt
+  steers the model to pick one (single tool call per turn).
+- **`on_job_response` interception**: the worker overrides this hook to
+  translate reviewer responses into `add_note` commands — the peers don't
+  know they're driving a UI; the worker mediates.
+
+## What's new vs. the prior demos
+
+| Prior demo | Pattern |
+|---|---|
+| hello-snapshot | snapshot streaming, voice/UI delegation |
+| pointing | scroll + multi-highlight |
+| deixis | bidirectional text selection |
+| form-fill | fills + click |
+| async-tasks | job-group fan-out + cancel |
+
+This one stitches all five together, plus the two patterns no prior demo
+touched: a **custom UI command** (`add_note`) and a **custom
+client-emitted event** (`note_click`).
+
+## Run
+
+Two terminals.
+
+**Terminal 1 — bot:**
+
+```bash
+cd examples/multi-worker/ui-worker/document-review
+uv run python bot.py
+```
+
+The bot starts on `http://localhost:7860`.
+
+**Terminal 2 — client:**
+
+```bash
+cd examples/multi-worker/ui-worker/document-review/client
+npm install            # one-time
+npm run dev
+```
+
+Open `http://localhost:5173` and click **Connect**.
+
+## What to try
+
+The article is a 6-paragraph draft seeded with one too-dense paragraph,
+one too-vague one, and one with absolutist tone problems.
+
+**Review flow (the centerpiece):**
+
+- Select the run-on paragraph, say _"review this."_ — the worker
+  acknowledges, the in-flight card appears, both reviewers tick through
+  progress, and two notes attach to the paragraph (clarity flags the
+  density).
+- Select the absolutist paragraph, say _"give me feedback."_ — tone
+  flags the strong words.
+
+**Notes flow:**
+
+- _"Add a note that this paragraph is too jargony."_ (with a paragraph
+  selected) — the worker fills the textarea and clicks Save.
+- Click any note in the panel — the page scrolls and selects the
+  paragraph it was attached to.
+
+**Navigation:**
+
+- _"Where does it talk about structured rhythms?"_ — the worker jumps to
+  the paragraph by selecting it.
+
+**Cancellation:**
+
+- During a review, click Cancel on the in-flight card. The reviewers'
+  responses come back as `cancelled`; feedback that already arrived stays
+  as a note.
+
+## Requirements
+
+- `OPENAI_API_KEY`
+- `DEEPGRAM_API_KEY`
+- `CARTESIA_API_KEY`
+
+A `.env` in the example folder is the easiest way to set these (see
+`examples/multi-worker/env.example`).
+
+## What this example does _not_ show
+
+Real worker integrations (the reviewers compute simple text metrics — for
+real LLM reviewers, swap them for `LLMWorker` subclasses whose
+`on_job_request` runs the LLM with the paragraph text and a critique
+prompt; everything else stays the same), note persistence, or
+multi-document / multi-page flows.