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.

internal/ui/dump_test.go

@@ -0,0 +1,118 @@
+package ui
+
+import (
+	"strings"
+	"testing"
+)
+
+const sampleDump = `<?xml version='1.0' encoding='UTF-8' standalone='yes' ?>
+<hierarchy rotation="0">
+  <node index="0" text="" class="android.widget.FrameLayout" package="com.tailscale.ipn" clickable="false" enabled="true" scrollable="false" bounds="[0,0][1080,2400]">
+    <node index="0" text="samuelrolfe@gmail.com" class="android.widget.TextView" package="com.tailscale.ipn" clickable="false" enabled="true" bounds="[221,155][798,217]"/>
+    <node index="1" text="Connected" class="android.widget.TextView" package="com.tailscale.ipn" clickable="false" enabled="true" bounds="[221,217][453,277]"/>
+    <node index="2" text="" content-desc="Navigate up" class="android.widget.ImageButton" package="com.tailscale.ipn" clickable="true" enabled="true" bounds="[42,121][189,268]"/>
+  </node>
+  <node index="1" text="Network and internet" class="android.widget.TextView" package="com.android.settings" clickable="true" enabled="true" bounds="[221,663][748,727]">
+    <node index="0" text="Network and internet" class="android.widget.TextView" package="com.android.settings" clickable="false" enabled="true" bounds="[221,663][748,727]"/>
+  </node>
+  <node index="2" text="Disabled thing" class="android.widget.TextView" package="com.android.settings" clickable="true" enabled="false" bounds="[0,0][10,10]"/>
+</hierarchy>`
+
+func parseSample(t *testing.T) *Hierarchy {
+	t.Helper()
+	h, err := parseHierarchy([]byte(sampleDump))
+	if err != nil {
+		t.Fatalf("parseHierarchy: %v", err)
+	}
+	return h
+}
+
+func TestBoundsAndCenter(t *testing.T) {
+	n := &Node{Bounds: "[221,155][798,217]"}
+	r, err := n.BoundsRect()
+	if err != nil {
+		t.Fatalf("BoundsRect: %v", err)
+	}
+	if r.X1 != 221 || r.Y1 != 155 || r.X2 != 798 || r.Y2 != 217 {
+		t.Fatalf("unexpected rect %+v", r)
+	}
+	cx, cy, err := n.Center()
+	if err != nil {
+		t.Fatalf("Center: %v", err)
+	}
+	if cx != (221+798)/2 || cy != (155+217)/2 {
+		t.Fatalf("unexpected centre (%d,%d)", cx, cy)
+	}
+}
+
+func TestBoundsRejectsGarbage(t *testing.T) {
+	for _, bad := range []string{"", "nope", "[1,2][3,4]junk", "[10,10][10,20]"} {
+		if _, err := (&Node{Bounds: bad}).BoundsRect(); err == nil {
+			t.Fatalf("expected error for bounds %q", bad)
+		}
+	}
+}
+
+func TestFindTextExactAndSubstring(t *testing.T) {
+	h := parseSample(t)
+
+	if got := len(h.FindText("Connected", true)); got != 1 {
+		t.Fatalf("exact match: want 1, got %d", got)
+	}
+	// Substring is case-insensitive and matches more than one node.
+	if got := len(h.FindText("network", false)); got != 2 {
+		t.Fatalf("substring match: want 2 (parent + child), got %d", got)
+	}
+	// Content descriptions count as text.
+	matches := h.FindText("Navigate up", true)
+	if len(matches) != 1 || !matches[0].Clickable {
+		t.Fatalf("content-desc match failed: %+v", matches)
+	}
+	if got := h.FindText("does not exist", false); got != nil {
+		t.Fatalf("expected no matches, got %d", len(got))
+	}
+}
+
+func TestPickBestMatchPrefersClickable(t *testing.T) {
+	h := parseSample(t)
+	matches := h.FindText("network", false)
+	if len(matches) != 2 {
+		t.Fatalf("want 2 matches, got %d", len(matches))
+	}
+	best, err := pickBestMatch(matches)
+	if err != nil {
+		t.Fatalf("pickBestMatch: %v", err)
+	}
+	if !best.Clickable {
+		t.Fatalf("expected a clickable match, got %s", best.Label())
+	}
+}
+
+func TestPickBestMatchRejectsDisabledOnly(t *testing.T) {
+	h := parseSample(t)
+	matches := h.FindText("Disabled thing", true)
+	if len(matches) != 1 {
+		t.Fatalf("want 1 match, got %d", len(matches))
+	}
+	if _, err := pickBestMatch(matches); err == nil {
+		t.Fatal("expected an error when the only match is disabled")
+	}
+}
+
+func TestEscapeInputText(t *testing.T) {
+	cases := map[string]string{
+		"hello world":    "'hello%sworld'",
+		"Rolling Stones": "'Rolling%sStones'",
+		"it's":           `'it'\''s'`,
+	}
+	for in, want := range cases {
+		if got := escapeInputText(in); got != want {
+			t.Errorf("escapeInputText(%q) = %q, want %q", in, got, want)
+		}
+	}
+	// A single quote must not be able to break out of the quoting.
+	got := escapeInputText("a'; rm -rf /; 'b")
+	if strings.Count(got, "'")%2 != 0 {
+		t.Fatalf("unbalanced quotes in %q", got)
+	}
+}