feat(examples): add sample-app spec

Introduce examples/sample-app/spec.ts — a minimal property-based spec that
taps the sample app's "Click me" button and asserts click_count is
monotonic. Bundle-check and the trace writer test now reference the new
path.

cmd/internal-tools/bundle-check/main.go

@@ -17,11 +17,7 @@ func main() {
 	specApiPath := filepath.Join(repoRoot, "pkg/spec-api/src/index.ts")
 
 	result, err := bundler.Bundle(bundler.Options{
-		EntryFile: "examples/specs/merchant-ledger.ts",
-		Defines: map[string]string{
-			"UATU_TEST_PHONE": "+910000000000",
-			"UATU_TEST_OTP":   "000000",
-		},
+		EntryFile: "examples/sample-app/spec.ts",
 		Aliases: map[string]string{
 			"@uatu/spec": specApiPath,
 		},