fix(mobile): Bug2 animation, trapped, border handling, and docstrings

[petercorke]

What

Bug2.py (entries 23-25 of the typing-pass problem list, h = None, and what a review of the file turned up).

Bugs fixed (each test failed first)

• run(animate=True) raised on current Matplotlib: set_data was given the 1-D start point on the first frame.
• run() without animation drew a marker at the grid origin on the current axes (and could create a figure). The artists are now made only when animating.
• next() called plt.show(block=True) before raising "robot is trapped", which blocks a script (entry 25).
• The movie argument implied animate but no movie was written; it now uses MovieWriter.
• run(**kwargs) swallowed unknown arguments. fig5_5.py passes label='path'; label is now a real argument that names the trail in the legend (default "robot path"), and anything else is a TypeError.
• start == goal gave a division by zero in hom_line and a RuntimeWarning.
• plot_m_line ignored its style for a vertical m-line. It now forwards *args, **kwargs to plot, so plot_m_line("r-") and plot_m_line(color="g") both work.
• edgelist / adjacent_point wrapped around at the left and top borders and raised at the right and bottom. The area outside the image is now outside the blob. The paths for the house floorplan (both directions) and map1 are identical before and after.
• Bare except: clauses (entry 24), the unused h, d, l, y, and dir shadowing the builtin are removed.

Docstrings and types

Path is ndarray(N,2) (it said (2,N)), m_line is R3, the direction names were wrong (NW twice), a mangled author list, :type current: for trail, and hom_line was undocumented.

Behaviour change: a diagonal crossing of the m-line is now seen

Bug2 reported "robot is trapped" when the m-line passed exactly through block corners at 45 degrees. The crossing test was abs(inner) <= 0.5 cells, but a line at 45 degrees to the grid passes between two diagonal neighbours at 0.707 from each, so the robot could step over it without ever being within half a cell. The tolerance is now sqrt(2)/2 (plus 1e-9 for rounding, since a diagonal neighbour is exactly that far away).

Effect on existing paths, measured: of the book cases (house floorplan both ways, map1) and three block cases, only one path changes: the house floorplan, bedroom to kitchen (Fig 5.5), from 1307 points to 1306. kitchen -> br3 (3985), map1 (334) and the straight and shallow block paths are identical.

The published number 1307 therefore needs an erratum. The change is documented in the run docstring (.. versionchanged:: 1.4.5) and a test pins the new length.

Notes for the book scripts (petercorke/RVC3-python#55)

• fig5_5.py passes label='path', which now takes effect (legend text "path" instead of "robot path").
• The Fig 5.5 path is 1306 points rather than 1307 (see above); the route is otherwise the same.

Full suite 1065 passed (with both compiled extensions), mypy clean.

🤖 Generated with Claude Code

[codacy-production]

Not up to standards ⛔

🔴 Issues 2 high

Alerts:
⚠ 2 issues (≤ 0 issues of at least minor severity)

Results:
2 new issues

Category	Results
ErrorProne	1 high
Security	1 high

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🟢 Metrics 42 complexity · 0 duplication

Metric	Results
Complexity	42
Duplication	0

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[codecov]

Codecov Report

❌ Patch coverage is 0% with 50 lines in your changes missing coverage. Please review.
✅ Project coverage is 0.00%. Comparing base (ec1e3fe) to head (1ce93fe).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/roboticstoolbox/mobile/Bug2.py	0.00%	50 Missing ⚠️

Additional details and impacted files

@@          Coverage Diff          @@
##            main    #780   +/-   ##
=====================================
  Coverage   0.00%   0.00%           
=====================================
  Files        144     144           
  Lines      14729   14733    +4     
=====================================
- Misses     14729   14733    +4     

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