[Bug] Mission start command sets idle after reboot instead of takeoff

[tstastny]

Describe the bug

Ok - so this is a real one. I thought I just messed up some branches / versions etc last time I caught this, but it happened again.
#21358 (comment)

Title describes it. Leads to runaway.

Sets IDLE position setpoint type instead of takeoff.

My guess is some bug in navigator on that command, not setting the right item for some reason .. and then secondary issue on fixedwing position controller that holds the last throttle command (which was initialized to cruise throttle in position mode) -- but need to investigate further.

To Reproduce

I haven't been able to reliably reproduce yet. This is only second time I've seen it. But order of operations:

1. make px4_sitl gazebo-classic_plane
2. make a mission with a takeoff
3. slide for takeoff in QGC
4. let it finish the mission
5. dont delete the mission if it asks you to
6. kill the sim
7. make px4_sitl gazebo-classic_plane
8. dont delete the mission if it asks you to
9. slide for takeoff in QGC
10. plane will keep cruise throttle but set IDLE mode position setpoint type

Expected behavior

Should set takeoff item, and takeoff properly.

Screenshot / Media

No response

Flight Log

https://review.px4.io/plot_app?log=9bfc46e9-82f4-450f-af9c-c0dcceb82615

Software Version

main - was testing fix branch.

Flight controller

sim

Vehicle type

Fixed Wing

How are the different components wired up (including port information)

No response

Additional context

No response

[DronecodeBot]

This issue has been mentioned on Discussion Forum for PX4, Pixhawk, QGroundControl, MAVSDK, MAVLink. There might be relevant details there:

https://discuss.px4.io/t/px4-maintainers-call-september-12-2023/34150/1

[sfuhrer]

I was able to reproduce following your guide above. Got an additional warning message: No valid mission available, refusing takeoff (which it then obviously didn't refuse).