Merges FN-3139 planning comment infrastructure (comment inputs in mission/milestone-slice/planning modals, comment display in conversation history), FN-3119 Quick Chat FAB with slash-triggered skill menu and plugin integration, FN-3117 plugin dashboard views and chat session icons, and FN-3066 plugi
Fusion-Task-Id: FN-3139
- Persist per-turn thinking output for planning and mission interview sessions, including history serialization and recovery-safe state fields
- Add shared conversation history parsing/API types and a reusable timeline component with formatted answers and expandable AI reasoning
- Restore and render conversation history across Planning Mode, Mission Interview, and Subtask Breakdown modals during resume and live question flow
- Harden response submission with nullable-question guards and expand unit/e2e coverage for history rendering and persistence behavior
