BUG: sample StochasticFlight inputs once per simulation (#1090)

[thatrandomasiandev]

Pull request type

• Code changes (bug fix, features)

Checklist

• Tests for the changes have been added (if needed)
• Docs have been reviewed and added / updated
• Lint (black rocketpy/ tests/ / make lint) has passed locally
• All tests (pytest tests -m slow --runslow) have passed locally
• CHANGELOG.md — no action needed; an LLM workflow auto-updates it after merge

Current behavior

MonteCarlo.__run_single_simulation called _randomize_rail_length, _randomize_inclination, and _randomize_heading, each of which invoked next(self.dict_generator()). One simulation therefore drew three times; the Flight mixed values across draws while last_rnd_dict (and .inputs.txt) kept only the last draw. StochasticFlight.create_object had the same pattern for rail_length.

Fixes #1090

New behavior

StochasticFlight._sample_flight_inputs() performs a single draw. create_object and MonteCarlo.__run_single_simulation both use that helper so flown rail/inclination/heading match last_rnd_dict. The _randomize_* helpers remain for single-field callers and still each draw once.

Breaking change

• No

Additional information

Focused unit tests assert create_object and __run_single_simulation Flight inputs equal last_rnd_dict. Full slow suite not run in this contribution pass.

[codecov]

Codecov Report

❌ Patch coverage is 72.72727% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 82.53%. Comparing base (e0ff281) to head (f6bc82c).
⚠️ Report is 43 commits behind head on develop.

Files with missing lines	Patch %	Lines
rocketpy/stochastic/stochastic_flight.py	50.00%	3 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1126      +/-   ##
===========================================
+ Coverage    82.18%   82.53%   +0.34%     
===========================================
  Files          122      128       +6     
  Lines        16355    16619     +264     
===========================================
+ Hits         13441    13716     +275     
+ Misses        2914     2903      -11     

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