refactor(agent): remove legacy in-process backend, rename harnesses pi_core/pi_agenta - #4833

32 tests  ±0   32 ✅ ±0   11s ⏱️ ±0s
 1 suites ±0    0 💤 ±0 
 1 files   ±0    0 ❌ ±0 

Results for commit 3cb0a64. ± Comparison against earlier commit 0e71bd0.