refactor(spec): one candidate producer over one target-eligibility rule

Both hosts routed verbs themselves and both policies enumerated their own
actions, and all four drifted. Web sent `swipes` to scrollable containers only,
so swipe-to-dismiss on a list row was reachable on native and unreachable on
web; the model policy folded gestures its own way and could not reach what the
seeded picker drew.

A host now reports facts about every element and never decides which verb may
act on it: targets.ts acceptsTarget owns that for both. pick.ts builtinCandidates
is the single enumeration, and the model policy reads it through
__sanderlingEnumerateBuiltin__ instead of reimplementing it in Go.

Gesture verbs change with it: scrolls stay vertical over scrollable containers,
swipes go free-form in all four directions from any element with real bounds.

Claude-Session: https://claude.ai/code/session_01Fj4wJUikdABuMQEETwW55J

internal/verifier/worker_test.go

@@ -1,24 +1,45 @@
 package verifier
 
 import (
+	"slices"
 	"testing"
 
 	"github.com/priyanshujain/sanderling/internal/hierarchy"
 )
 
-// TestVerbAcceptsSwipeRequiresPositiveBounds locks the fix for the notification
-// shade: a zero-bounds element centers at (0,0), and a downward swipe from the
-// top-left corner is the system gesture that pulls the shade over the app. The
-// swipe verb must reject zero-bounds nodes like every other verb does.
-func TestVerbAcceptsSwipeRequiresPositiveBounds(t *testing.T) {
-	zeroBounds := &hierarchy.Element{Bounds: hierarchy.Bounds{}}
-	if verbAccepts("swipes", zeroBounds) {
-		t.Error("swipes must reject a zero-bounds element (it centers at (0,0) and pulls the notification shade)")
+// TestTargetsReportFactsWithoutFiltering pins the native host's half of the
+// split introduced to stop the two hosts drifting: it reports what an element
+// IS and never decides which verb may act on it. The verb decision is one shared
+// rule (pkg/spec/src/targets.ts) both hosts consume, asserted across engines by
+// TestHostsAgreeOnTargetEligibility.
+func TestTargetsReportFactsWithoutFiltering(t *testing.T) {
+	tree, err := hierarchy.Parse(hostParityTreeJSON)
+	if err != nil {
+		t.Fatal(err)
 	}
-
-	realBounds := &hierarchy.Element{Bounds: hierarchy.Bounds{Left: 100, Top: 400, Right: 980, Bottom: 600}}
-	if !verbAccepts("swipes", realBounds) {
-		t.Error("swipes must accept an element with positive bounds")
+	v := &Verifier{lastTree: tree}
+	targets := v.targets()
+	if len(targets) != len(hostParityScreen) {
+		t.Fatalf("targets() returned %d elements, want all %d in the tree",
+			len(targets), len(hostParityScreen))
+	}
+	for index, target := range targets {
+		want := hostParityScreen[index]
+		got := []bool{
+			target.clickable, target.enabled, target.editable, target.scrollable,
+		}
+		expected := []bool{
+			want.clickable, want.enabled, want.editable, want.scrollable,
+		}
+		if !slices.Equal(got, expected) {
+			t.Errorf("%s clickable/enabled/editable/scrollable = %v, want %v",
+				want.name, got, expected)
+		}
+		positiveBounds := target.width > 0 && target.height > 0
+		if positiveBounds != want.positiveBounds {
+			t.Errorf("%s positive bounds = %v, want %v",
+				want.name, positiveBounds, want.positiveBounds)
+		}
 	}
 }