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

160 tests  ±0   160 ✅ ±0   1s ⏱️ ±0s
 25 suites ±0     0 💤 ±0 
  1 files   ±0     0 ❌ ±0 

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