fix(blocks): DiffSteer NameError and VehiclePlot shared defaults, with types and docstrings

[petercorke]

What

A fix and a review of blocks/mobile.py (the bdsim vehicle blocks).

Bugs fixed

• DiffSteer() without x0 raised NameError (slef for self), so the block could not be created with its default. Bicycle and Unicycle were fine.
• VehiclePlot had mutable default arguments (polyargs={}, labels=[...]) and updated polyargs in place, so a size given to one VehiclePlot leaked into every later one.
• VehiclePlot(scale=<ndarray>) crashed on scale != "auto". Any sequence is accepted now; a [min, max] applies to both axes.
• x0 was checked with an assert (skipped under -O) and stored as given. It is now converted and checked with base.getvector: a wrong length is a ValueError and the state is always an ndarray.
• A leftover print("done") in VehiclePlot.start is removed.

Removed

The unused a argument of the DiffSteer block. Nothing in RTB or the RVC3 notebooks and figure scripts passes it.

Types and docstrings

• ArrayLike3, R3, float, Callable[[Axes], None] and bdsim's SimulationState replace Any.
• Wrong documented defaults for the DiffSteer block (speed_max, steer_max), "Inital", a misspelt class reference, .. deprecated:: with its version (1.4.0), redundant :type: lines removed, :raises: added.

Testing

Ten new tests in MobileBlockTest, each of which failed before its fix. The vehicle-block calls in the RVC3 figure scripts still work (x0 as list or array, scale=[0, 10], size, shape, init). mypy is clean.

Renamed (old names deprecated, still work)

VehiclePlot: path → path_style, init → init_func, scale → limits (it is the axis limits, and clashed with VehiclePolygon's scale, the vehicle size), polyargs → polygon_style. See petercorke/rvc-ecosystem#15 for the convention.

🤖 Generated with Claude Code

[codacy-production]

Not up to standards ⛔

🔴 Issues 1 high

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

Results:
1 new issue

Category	Results
Security	1 high

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🟢 Metrics 82 complexity · 13 duplication

Metric	Results
Complexity	82
Duplication	13

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[codecov]

Codecov Report

❌ Patch coverage is 0% with 49 lines in your changes missing coverage. Please review.
✅ Project coverage is 0.00%. Comparing base (2ee9fa9) to head (b2e4f03).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/roboticstoolbox/blocks/mobile.py	0.00%	49 Missing ⚠️

Additional details and impacted files

@@          Coverage Diff          @@
##            main    #775   +/-   ##
=====================================
  Coverage   0.00%   0.00%           
=====================================
  Files        143     143           
  Lines      14663   14671    +8     
=====================================
- Misses     14663   14671    +8     

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