fix(navigator): invalidate next setpoint when waypoint yaw is not aligned

[Luka-Filipovic]

Solved Problem

When a rotary wing waypoint requires yaw alignment, the next position setpoint
remains valid during approach. This causes FlightTaskAuto to plan a fly-through
trajectory instead of decelerating, so the vehicle overshoots the waypoint
before aligning yaw.

Solution

• Invalidate next.valid when the current waypoint requires yaw acceptance,
  and re-enable it dynamically once yaw is aligned (_next_sp_awaits_yaw).
• Evaluate yaw alignment independently of position reached, so yaw can be
  checked during approach. Once both position and yaw are reached the state
  latches to avoid interfering with hold time. This keeps the existing logic unchanged.

Changelog Entry

Bugfix: Multicopter missions now brake at waypoints requiring yaw alignment

Alternatives

Test coverage

TODO