Add pointing UIWorker example

The voice LLM delegates to a ReplyToolMixin UIWorker that scrolls offscreen
items into view and highlights the phones it names — exercising the scroll_to /
highlight UI commands and the [offscreen] state tag.

examples/multi-worker/ui-worker/pointing/README.md

@@ -0,0 +1,81 @@
+# pointing
+
+The UIWorker finds items on the page and points at them. A grid of
+phone listings tall enough that several rows sit below the fold; the
+user asks for one by name and the worker scrolls it into view and
+flashes it.
+
+## What it shows
+
+- The `scroll_to` and `highlight` UI commands round-tripping
+  end-to-end: the `UIWorker` emits them, the native bridge in
+  `PipelineWorker` translates them to RTVI frames, and the client
+  handler resolves the snapshot ref and acts on the live DOM.
+- `ReplyToolMixin`'s visual fields — `reply(answer, scroll_to=...,
+  highlight=[...])`. One tool call per turn; `answer` is required so
+  the model can't forget the spoken reply.
+- The `[offscreen]` state tag the client emits, and the LLM reading it
+  to decide whether a scroll is needed before highlighting.
+
+## What it adds vs. `hello-snapshot`
+
+`hello-snapshot` proved the worker can *read* the page. This one proves
+it can *act* on the page. Same skeleton (voice LLM in the main pipeline
+delegating to a `UIWorker` via a `respond` job); the new parts are the
+`scroll_to` / `highlight` commands and the client handlers for them.
+
+## Run
+
+Two terminals.
+
+**Terminal 1 — bot:**
+
+```bash
+cd examples/multi-worker/ui-worker/pointing
+uv run python bot.py
+```
+
+The bot starts on `http://localhost:7860`.
+
+**Terminal 2 — client:**
+
+```bash
+cd examples/multi-worker/ui-worker/pointing/client
+npm install            # one-time
+npm run dev
+```
+
+Open `http://localhost:5173` and click **Connect**.
+
+## What to try
+
+The page renders 20 phone cards in a responsive grid; the bottom rows
+usually land below the fold. Try:
+
+- _"Where's the iPhone 17?"_ — the worker scrolls the card into view and
+  flashes it.
+- _"Scroll to the Pixel 9 Pro."_ — same flow, different ref.
+- _"Which one is the Nothing phone?"_ — if it's already visible, the
+  worker just highlights without scrolling.
+- _"Which phones are from Google?"_ — a descriptive question; the worker
+  highlights each phone it names.
+- _"What's the cheapest one?"_ — the worker names and highlights it.
+
+Watch the bot logs: each turn shows the main LLM calling
+`answer_about_screen`, then the UIWorker's LLM emitting one `reply`
+(scroll/highlight + the spoken answer).
+
+## 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 _doesn't_ show
+
+Form filling (see `form-fill/`), selection-based deixis (see `deixis/`),
+async task cards (see `async-tasks/`), or custom command handlers beyond
+the standard `scroll_to` / `highlight`.