Merged PlanningModeModal swipe-back and New Session handling: the feature commits wire key swipe-back gestures to control mobile detail-pane visibility and document the nav trigger rule, while the test commit adds coverage for New Session and mobile swipe-back regressions.
Fusion-Task-Id: FN-4187
Implements swipe-back gesture support for mobile navigation across ChatView, MissionManager, and PlanningModeModal, wired through a shared navigation history context and covered by a comprehensive test suite (~548 lines of swipe-back tests). A small fixup ensures swipe-back behaves correctly when la
Fusion-Task-Id: FN-4139