Fix coverage with several contract classes; table annotation and file path checks; clean task dir on write

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014aUaQeLnwbb1zTpN7kHeat

tasks_gen/eval/G0116/generation.json

@@ -0,0 +1,19 @@
+{
+ "id": "G0116",
+ "pool": "eval",
+ "object_type": "CLAS",
+ "category": "C",
+ "attempts": [
+  {
+   "stage": "validate",
+   "oracle": 100.0,
+   "null": 0,
+   "mutation": {
+    "valid": 5,
+    "killed": 5,
+    "ok": true
+   }
+  }
+ ],
+ "accepted": true
+}