Pylance: type UAV vehicle state

[ethayu]

Scope

Pyright/Pylance reports vehicle-state diagnostics in the UAV vehicle layer:

• nullable UAV position/yaw state is used before narrowing
• payload runtime node extensions are accessed through the base ROS Node type
• vision node helper names/services are read dynamically from object

Acceptance

• Focused Pyright is clean for uav/vehicles/UAV.py, uav/vehicles/Payload.py, and uav/vehicles/Vehicle.py
• Vehicle state access is guarded before use instead of relying on unchecked nullable fields
• Payload runtime node extensions are represented with a structural type
• Ruff check and format pass for touched files

Part of #201

[ethayu]

Resolved by consolidated PR #231 and tracked under parent #201. Closing this leaf issue after issue/PR condensation.