Add show parameter to .pl.show() to control plt.show() behavior

[timtreis]

Summary

• Adds a show: bool | None = None parameter to .pl.show() so users can prevent plt.show() from being called.
• When running scripts, plt.show() was called unconditionally (clearing the figure before plt.savefig()). With show=False, users can now save or further modify the figure.
• Default (None) preserves current auto-detection behavior via sys.ps1.

Closes #494

Before (script)

fig, axs = plt.subplots(ncols=2)
axs[0].plot([1, 2, 3, 4], [1, 2, 3, 4])
sdata.pl.render_images("blobs_image").pl.show(ax=axs[1])
plt.savefig("test.png")  # blank image — plt.show() already cleared it

After

fig, axs = plt.subplots(ncols=2)
axs[0].plot([1, 2, 3, 4], [1, 2, 3, 4])
sdata.pl.render_images("blobs_image").pl.show(ax=axs[1], show=False)
plt.savefig("test.png")  # works as expected

Behavior matrix

show=	Interactive (Jupyter)	Script (.py)
None (default)	no plt.show()	plt.show() (same as before)
True	plt.show()	plt.show()
False	no plt.show()	no plt.show()

Test plan

• show=False prevents plt.show(), saved image is not blank
• show=None preserves current behavior
• show=True always calls plt.show()
• Invalid value (e.g. show="yes") raises TypeError
• Pre-commit hooks pass (prettier, ruff, ruff format, mypy)

🤖 Generated with Claude Code

[codecov-commenter]

Codecov Report

❌ Patch coverage is 80.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 83.83%. Comparing base (d7dc3f0) to head (abe6be6).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
src/spatialdata_plot/pl/utils.py	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #537      +/-   ##
==========================================
+ Coverage   83.74%   83.83%   +0.08%     
==========================================
  Files           8        8              
  Lines        2553     2573      +20     
==========================================
+ Hits         2138     2157      +19     
- Misses        415      416       +1     

Files with missing lines	Coverage Δ
src/spatialdata_plot/pl/basic.py	91.66% <100.00%> (+0.11%)	⬆️
src/spatialdata_plot/pl/utils.py	79.30% <50.00%> (-0.04%)	⬇️

... and 2 files with indirect coverage changes

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[LucaMarconato]

I wonder if it closes #68

[timtreis]

I added another check for matplotlib.is_interactive() which allegedly covers PyCharm, but I don't use PyCharm, could you verify?