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/G0122/generation.json

@@ -0,0 +1,29 @@
+{
+ "id": "G0122",
+ "pool": "eval",
+ "object_type": "FUNC",
+ "category": "C",
+ "attempts": [
+  {
+   "stage": "validate",
+   "oracle": null,
+   "null": null
+  },
+  {
+   "stage": "validate",
+   "oracle": 0,
+   "null": 0
+  },
+  {
+   "stage": "validate",
+   "oracle": 0,
+   "null": 0
+  },
+  {
+   "stage": "validate",
+   "oracle": 0,
+   "null": 0
+  }
+ ],
+ "accepted": false
+}