feat(pvisor): add replay boundary prompts and Pi agent support

[wyeth93]

Summary

• add an optional one-shot boundary user prompt after the fresh replay observation and before the first live model inference
• add Pi agent 0.83.0 native RPC event replay for read, bash, edit, and write tool batches
• preserve agent-native continuation semantics and emit structured next-action comparisons
• document pVisor installation, CLI/TOML usage, Pi adaptation, and replay results

Validation

• cargo fmt --all -- --check
• UV_CACHE_DIR=/tmp/persisting-docs-uv-cache uv run mkdocs build --strict
• targeted cargo test was attempted, but the local crates.io index timed out and offline resolution lacked locked fastrand 2.4.1 metadata; main-repository Pre-CI will run the clean dependency test suite