Merge PR #128: inflight tracking + fixes

Merge feat/inflight-tracking with conflict resolution.
Fixes applied:
- inflight.rs: replace unwrap() with poison-safe lock handling
- tools.rs: move inflight.add() inside Prepared arm only, avoiding
  wasteful add-then-immediate-delete for Immediate outcomes
- run.rs: wire inflight through execute_tool_calls_with to both
  sequential and parallel dispatch paths, remove dead import

Author: Yogthos