test(rules): add integration test evidence

- All 11 rule files verified (exist, under limits)
- Full lib integration verified (11 paths returned)
- Context budget verified (975 < 1500)
- All instruction paths resolve to real files
- opencode.nix rules entry verified

Refs: T17 of rules-system plan

.sisyphus/evidence/task-17-budget.txt

@@ -0,0 +1,6 @@
+=== Context Budget ===
+Concerns: 751
+Python: 224
+Total (concerns + python): 975
+Limit: 1500
+RESULT: PASS (under 1500)