feat: Phase 2 act primitives

Add the Artemis Go CLI and its packages:
- internal/adb: timeout-bounded adb wrapper, device list, wireless-debugging
  port scan and auto-connect (never hardcodes the moving port).
- internal/ui: uiautomator dump parsing, find-by-text, tap the centre of a
  text match (FR-4), type, swipe, scroll, back, home, launch, wake.
- cmd/artemis: CLI for the primitives plus 'demo', the Phase 2 DoD run.

Failures are loud: a missing or disabled element errors instead of tapping a
guessed coordinate. The screen is woken before acting, and every adb call has
a deadline.

Also record the section 13 Q4 decision (adb lives in the user profile on .13,
wireless ADB needs no udev rules; service packaging still open until Phase 6),
add unit tests, and document the phase evidence.

README.md

@@ -0,0 +1,68 @@
+# Artemis Control
+
+Artemis is the phone's **hands**. It drives the Pixel 8a screen from `.13` over
+Tailscale using **ADB wireless**, so the Hub can do things no deep link allows.
+
+The build spec is [`AGENTS.md`](AGENTS.md). Follow the phases in section 11 in
+order.
+
+## Status
+
+| Phase | State |
+|---|---|
+| 1 — Prove the ADB link | ✅ proven — see [`docs/phase-1-adb-link.md`](docs/phase-1-adb-link.md) |
+| 2 — Act primitives | ✅ done — tap by text, type, scroll, back, home, launch |
+| 3 — Spotify recipe | not started |
+| 4 — Song radio | not started |
+| 5 — Maps recipe | not started |
+| 6 — Action API | not started |
+| 7 — Resilience | not started |
+| 8 — Documentation | not started |
+
+## Layout
+
+```
+cmd/artemis/        command line entry point
+internal/adb/       timeout-bounded wrapper around the adb binary
+internal/ui/        read the screen (uiautomator dump) and act on it (input)
+docs/               phase evidence and notes
+```
+
+## Build and test
+
+Go is not installed system-wide on `.13`; use a one-off nix shell. Nothing is
+added to `nixos-rebuild` and no system module changes.
+
+```sh
+nix shell nixpkgs#go -c go build -o bin/artemis ./cmd/artemis
+nix shell nixpkgs#go -c go vet ./...
+nix shell nixpkgs#go -c go test ./...
+```
+
+## Use
+
+The phone address defaults to `100.101.49.17`. Override with `ARTEMIS_PHONE`,
+pin a serial with `ARTEMIS_ADB_SERIAL`, or point at a different adb with
+`ARTEMIS_ADB`.
+
+```sh
+./bin/artemis connect          # scan for the wireless-debugging port, then connect
+./bin/artemis devices
+./bin/artemis dump             # text nodes and bounds
+./bin/artemis launch com.spotify.music
+./bin/artemis tap "Search"     # find by text, tap its centre (FR-4)
+./bin/artemis type "Rolling Stones Honky Tonk"
+./bin/artemis scroll down
+./bin/artemis back
+./bin/artemis home
+./bin/artemis demo             # Phase 2 DoD: launch an app, tap a named element
+```
+
+## Rules that the code enforces
+
+- **Find by text, never fixed coordinates.** `tap` resolves a text match to
+  bounds and taps the centre.
+- **Never tap blindly.** A missing or disabled element is a loud failure, not a
+  guessed coordinate.
+- **Wake first.** Every acting command wakes the screen (FR-7).
+- **Bound every command.** No adb call runs without a timeout (FR-11).