test: add JavaScript fixture and update comment pattern tests

tests/fixtures/watch.js

@@ -0,0 +1,27 @@
+// Regular AI comment
+//ai do something
+//AI make this better
+//ai! urgent change needed
+//AI! another urgent one
+// ai with space
+// AI with caps
+// ai! with bang
+// this is not an ai comment
+// aider is not an ai comment
+
+function dummyFunction() {
+    // ai inside function
+    return true;
+}
+
+class Example {
+    constructor() {
+        // ai in constructor
+        this.value = 42;
+    }
+
+    method() {
+        // ai in method
+        return this.value;
+    }
+}