TST: cover PyVista flight animation helpers and fix docstring

Fixes the two CI failures on the develop -> master sync (PR #1068):

- DOC/build-docs: the ``color_by`` parameter of ``animate_trajectory``
  used the numpydoc ``{...}`` value-set syntax split across two lines,
  which numpydoc rejects ("invalid value set (missing closing brace)").
  Because the docs job builds with ``-W`` (warnings as errors) the build
  failed. Rewrite the type as a single-line prose description.

- codecov/patch and codecov/project: the new PyVista animation subsystem
  in ``_FlightPlots`` was only exercised by a single minimal off-screen
  smoke test, leaving the scene builders and the pure geometry/telemetry
  helpers uncovered. Add unit tests for the render-independent helpers
  (quaternion rotation, polylines, camera paths, option validation, event
  markers, telemetry panels, background palette, etc.) and extend the
  off-screen integration tests to drive the full set of overlays (charts,
  camera tracking, stability markers, playback controls) and the GIF
  export path.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VW2VidZmPd93dd8xW8BX2J

Author: claude

rocketpy/plots/flight_plots.py

@@ -1265,9 +1265,10 @@ def animate_trajectory(  # pylint: disable=too-many-statements,too-many-locals
             Ground texture. A mapping may define ``image``, ``bounds``,
             ``coordinates`` (``"enu"`` or ``"latlon"``), and ``flip_y`` for
             geographic placement. Default is None.
-        color_by : {"speed", "mach", "dynamic_pressure", "acceleration",
-            "altitude", False, None}, optional
-            Trajectory point scalar. Default is "speed".
+        color_by : str | bool | None, optional
+            Trajectory point scalar, one of ``"speed"``, ``"mach"``,
+            ``"dynamic_pressure"``, ``"acceleration"``, ``"altitude"``,
+            ``False`` or ``None``. Default is "speed".
         show_kinematic_plots : bool, optional
             Show altitude, speed and acceleration histories. Default is False.
         camera_mode : {"static", "follow", "ground", "body"}, optional

tests/integration/test_plots.py

@@ -33,6 +33,64 @@ def test_flight_animations_run_off_screen(flight_calisto):
     assert rotation_result is None
 
 
+def test_flight_animations_render_all_scene_options(flight_calisto):
+    """Exercise the animation scene builders with the full set of overlays.
+
+    Rendering off screen with playback controls, charts, camera tracking and
+    stability markers enabled covers the scene-construction branches of both
+    ``animate_trajectory`` and ``animate_rotate`` (and the playback-control
+    setup in ``_run_animation``) that the minimal smoke test does not reach.
+    """
+    pytest.importorskip("pyvista")
+    shared_options = {
+        "start": 0,
+        "stop": None,  # spans the whole flight, hitting every event marker
+        "time_step": 2.0,
+        "backend": "none",
+        "off_screen": True,
+        "window_size": (240, 180),
+        "playback_controls": True,
+    }
+
+    trajectory_result = flight_calisto.plots.animate_trajectory(
+        **shared_options,
+        color_by="mach",
+        show_kinematic_plots=True,
+        show_subrocket_point=True,
+        camera_mode="follow",
+    )
+    rotation_result = flight_calisto.plots.animate_rotate(
+        **shared_options,
+        show_attitude_plots=True,
+        show_cp_cm=True,
+        camera_mode="body",
+    )
+
+    assert trajectory_result is None
+    assert rotation_result is None
+
+
+def test_flight_animation_export_gif(flight_calisto, tmp_path):
+    """Cover the deterministic GIF export path of ``_run_animation``."""
+    pytest.importorskip("pyvista")
+    pytest.importorskip("imageio")
+    export_file = tmp_path / "trajectory.gif"
+
+    result = flight_calisto.plots.animate_trajectory(
+        start=0,
+        stop=0.3,
+        time_step=0.1,
+        backend="none",
+        window_size=(240, 180),
+        color_by="speed",
+        export_file=str(export_file),
+    )
+
+    assert result == str(export_file)
+    assert export_file.is_file()
+    assert export_file.stat().st_size > 0
+
+
 @patch("matplotlib.pyplot.show")
 def test_compare(mock_show, flight_calisto):
     """Here we want to test the 'x_attributes' argument, which is the only one