Cleared queued tool-choice directives and ACP always decisions after successful logical session transitions.
Added new-session and cross-session regression coverage for staged resolves and both ACP always decisions.
Fixes#4093
- Extracted internal handlers and logic from AgentSession into dedicated runner, guard, and coordinator modules.
- Created standalone modules for bash execution, evaluation runners, IRC bridging, and prewalk coordination.
- Established dedicated session components for tracking stats, todos, streams, and retry fallback chains.
- Preserved existing session behavior while significantly reducing monolithic class size and complexity.