chengyongru a1e1eed2f1 refactor(runner): consolidate all injection drain paths and deduplicate tests
- Migrate "after tools" inline drain to use _try_drain_injections,
  completing the refactoring (all 6 drain sites now use the helper).
- Move checkpoint emission into _try_drain_injections via optional
  iteration parameter, eliminating the leaky split between helper
  and caller for the final-response path.
- Extract _make_injection_callback() test helper to replace 7
  identical inject_cb function bodies.
- Add test_injection_cycle_cap_on_error_path to verify the cycle
  cap is enforced on error exit paths.
2026-04-14 00:30:30 +08:00
..