feat(tree-sitter-overlay-extra): parse JS/C/Java overlay via optional extra

Add openultrasast[semantic] with official grammar wheels and one CST walker
into FileIR. quick stays extra-free. Host CLI is not overlay-ready. Default CI
stays extra-free; a semantic job runs pytest -m semantic.

.kiro/specs/tree-sitter-overlay-extra/spec.json

@@ -0,0 +1,22 @@
+{
+  "feature_name": "tree-sitter-overlay-extra",
+  "created_at": "2026-09-04T14:00:00Z",
+  "updated_at": "2026-09-04T15:00:00Z",
+  "language": "en",
+  "phase": "tasks-generated",
+  "approvals": {
+    "requirements": {
+      "generated": true,
+      "approved": true
+    },
+    "design": {
+      "generated": true,
+      "approved": true
+    },
+    "tasks": {
+      "generated": true,
+      "approved": true
+    }
+  },
+  "ready_for_implementation": true
+}