TST: cover controller behavior and reporting

[ting-hong-shieh]

Summary

Add focused unit coverage for controller state handling, reporting, and non-pickle serialization. The tests exercise observable behavior and complement the existing Flight integration coverage; they do not change production code.

This is a small contribution toward #709.

Coverage

Both measurements used the same non-slow unit, integration, and acceptance suite, followed by the RocketPy doctests.

Scope	Base cb6106a717207dd8fc2dfe1446d80ff75022f21b	Head 5a205109a6989a569d20e8ec448eba8c71c6ae1e
rocketpy/control/controller.py	54/63 (85.71%)	63/63 (100.00%)
rocketpy/prints/controller_prints.py	7/24 (29.17%)	22/24 (91.67%)
Entire rocketpy package	13,810/17,080 (80.8548%)	13,834/17,080 (80.9953%)

The new tests cover 24 previously missed statements. They verify:

• preservation of the initial observation and appending of each controller return value;
• discrete and continuous controller descriptions;
• reporting for one and multiple interactive objects;
• non-pickle serialization of the function name and interactive-object hashes; and
• restoration when from_dict() receives an existing callable.

Verification

$ pytest tests \
    --deselect tests/integration/test_plots.py::test_flight_animations_run_off_screen \
    --deselect tests/integration/test_plots.py::test_flight_animations_render_all_scene_options \
    --deselect tests/integration/test_plots.py::test_flight_animation_export_gif \
    --cov=rocketpy --cov-report=
2193 passed, 53 skipped, 3 deselected

$ pytest rocketpy --doctest-modules --cov=rocketpy --cov-append --cov-report=
48 passed

$ pytest tests/unit/control/test_controller.py \
    tests/unit/simulation/test_flight_time_nodes.py \
    tests/integration/simulation/test_flight.py -k controller
13 passed, 34 deselected

$ ruff check tests/unit/control/test_controller.py
All checks passed!

$ ruff format --check tests/unit/control/test_controller.py
1 file already formatted

The three PyVista animation tests were excluded locally because the first off-screen render terminated the local VTK process with a segmentation fault. The repository workflow already runs those three tests as a separate retrying step; the PR does not modify animation code.

Environment

• macOS 26.5.2, arm64
• Python 3.12.6
• RocketPy 1.13.0
• NumPy 2.5.2
• SciPy 1.18.0
• pytest 9.1.1
• Ruff 0.16.3

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.45%. Comparing base (e0ff281) to head (e174742).
⚠️ Report is 59 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1152      +/-   ##
===========================================
+ Coverage    82.18%   83.45%   +1.26%     
===========================================
  Files          122      130       +8     
  Lines        16355    17082     +727     
===========================================
+ Hits         13441    14255     +814     
+ Misses        2914     2827      -87     

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[Gui-FernandesBR]

does it really increase the test coverage? How many lines?