ENH: Restore power_off/on_drag as Function objects; add _input attributes for raw user input and update changelog

[Copilot]

Pull request type

• Code changes (bugfix, features)
• Code maintenance (refactoring, formatting, tests)
• ReadMe, Docs and GitHub updates
• Other (please describe):

Checklist

• Tests for the changes have been added (if needed)
• Docs have been reviewed and added / updated
• Lint (black rocketpy/ tests/) has passed locally
• All tests (pytest tests -m slow --runslow) have passed locally
• CHANGELOG.md has been updated (if relevant)

Current behavior

Rocket.power_off_drag and Rocket.power_on_drag had been changed to store raw user input, which broke backward compatibility because these public attributes were historically Function objects. This also created type inconsistency depending on construction path (for example, from_dict could still pass a Function).

New behavior

• Restores Rocket.power_off_drag and Rocket.power_on_drag as Mach-only Function objects (aliasing power_off_drag_by_mach and power_on_drag_by_mach) to preserve the public API.
• Preserves original user-provided drag inputs via new attributes:
  • power_off_drag_input
  • power_on_drag_input
• Updates related docstrings in:
  • rocketpy/rocket/rocket.py
  • rocketpy/rocket/point_mass_rocket.py
• Adds an Unreleased → Fixed changelog entry in CHANGELOG.md for this PR.

Breaking change

• Yes
• No

Additional information

This stacked PR targets rel/v1.12.0 and includes the follow-up changelog update requested in review feedback.

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[MateusStano]

@copilot add pr to changelog

[Copilot]

@copilot add pr to changelog

Done in e750b18. Added this PR to CHANGELOG.md under Unreleased → Fixed.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.06%. Comparing base (1618fb0) to head (e750b18).

Additional details and impacted files

@@             Coverage Diff              @@
##           rel/v1.12.0     #941   +/-   ##
============================================
  Coverage        81.05%   81.06%           
============================================
  Files              107      107           
  Lines            13891    13893    +2     
============================================
+ Hits             11260    11262    +2     
  Misses            2631     2631           

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[Gui-FernandesBR]

maybe?

Suggested change

	self.power_off_drag_input = power_off_drag
	self.power_on_drag_input = power_on_drag
	self._power_off_drag_input = power_off_drag
	self._power_on_drag_input = power_on_drag