test(js): cover fingerprint mismatch fallback

Assert the browser runtime refuses stale partial/effect updates when deployment fingerprints mismatch and falls back to reload instead of applying stale ids.

req: abi/003

req: abi/004

req: runtime/004

slhx-js/tests/runtime.rs

@@ -67,6 +67,19 @@ fn runtime_exposes_page_swap_hooks() {
     assert!(source.contains("location.href = href"));
 }
 
+#[test]
+fn runtime_refuses_partial_updates_on_fingerprint_mismatch() {
+    // req: abi/003 req: abi/004 req: runtime/004
+    let source = slhx_js::RUNTIME_JS;
+
+    assert!(source.contains("function compatibleFingerprint(response, root)"));
+    assert!(source.contains("const received = response.headers.get(\"x-slhx-fingerprint\")"));
+    assert!(source.contains("const expected = root && root.getAttribute(FINGERPRINT)"));
+    assert!(source.contains("if (!compatibleFingerprint(response, root))"));
+    assert!(source.contains("location.reload()"));
+    assert!(source.contains("if (expected && String(batch.fingerprint) !== expected)"));
+}
+
 #[test]
 fn runtime_page_swaps_lowered_slot_ids() {
     // req: wire/001