Surface tracking: preserve full pilot climb/descent authority

[lthall]

Summary

Surface tracking can currently saturate vertical rate limits, preventing the pilot from commanding climb or descent when terrain-following is active.

This change adjusts the pilot’s effective climb/descent limits based on the terrain-following command, ensuring the pilot always retains full vertical authority while still allowing terrain tracking to operate within the overall limits.

Board,antennatracker,blimp,bootloader,copter,heli,plane,rover,sub
CubeOrange,*,*,*,-104,-104,*,*,*

Classification & Testing (check all that apply and add your own)

• Checked by a human programmer
• Non-functional change
• No-binary change
• Infrastructure change (e.g. unit tests, helper scripts)
• Automated test(s) verify changes (e.g. unit test, autotest)
• Tested manually, description below (e.g. SITL)
• Tested on hardware
• Logs attached
• Logs available on request

[Copilot]

Pull request overview

Adjusts ArduCopter surface tracking integration so terrain-following no longer consumes the full vertical rate “budget” and blocks pilot climb/descent commands, preserving full net pilot authority while still respecting overall vertical limits.

Changes:

• Exposes terrain-following vertical velocity from AC_PosControl for use by pilot climb-rate mapping.
• Adjusts pilot climb/descent rate scaling based on current terrain-following vertical velocity contribution.
• Removes per-mode post-clamp of pilot climb rate that would negate the adjusted authority.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
libraries/AC_AttitudeControl/AC_PosControl.h	Adds accessor for terrain vertical velocity contribution (_vel_terrain_d_ms).
ArduCopter/Attitude.cpp	Adjusts pilot climb-rate curve to account for terrain-following velocity; adds adjusted pilot speed helpers.
ArduCopter/Copter.h	Declares adjusted pilot climb/descent limit helper methods.
ArduCopter/mode_althold.cpp	Removes post-constrain of pilot climb rate.
ArduCopter/mode_loiter.cpp	Removes post-constrain of pilot climb rate.
ArduCopter/mode_poshold.cpp	Removes post-constrain of pilot climb rate.
ArduCopter/mode_sport.cpp	Removes post-constrain of pilot climb rate.
ArduCopter/mode_flowhold.cpp	Removes post-constrain of pilot climb rate.
ArduCopter/mode_zigzag.cpp	Removes post-constrain of pilot climb rate.

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[be-ska]

@lthall log from #32740 (comment): 00000016.BIN.zip