fix: make CI tests self-sufficient, remove cost tests, rename workflow

- Delete test_cost_budget.py and test_medium_cost.py (require aur init)
- Fix policies test_engine.py to use tmp_path instead of relying on .aurora/
- Rename workflow from "Testing Infrastructure (New)" to "CI"

Author: hamr0

…workflows/testing-infrastructure-new.yml .github/workflows/ci.yml.github/workflows/testing-infrastructure-new.yml renamed to .github/workflows/ci.yml .github/workflows/testing-infrastructure-new.yml renamed to .github/workflows/ci.yml

@@ -1,4 +1,4 @@
-name: Testing Infrastructure (New)
+name: CI
 
 # Streamlined CI for direct-to-main workflow
 # - Single Python version (3.12)