Add .vsi/.qptiff/.zvi/.afi support via slideio

[rushin682]

Summary

• Add SlideioImageConverter, a third ImageConverter backend (alongside OpenSlide and Bioio) reading .vsi, .qptiff, .zvi, .afi via slideio. Streams level 0 through a new SlideioTiledSource, never materializing a full whole-slide plane in memory.
• slideio added as a required dependency (numpy-only wheels, BSD-3-Clause).
• OpenSlideImageConverter and SlideioImageConverter now raise if the source has no physical pixel size, instead of silently assuming 1.0 um/px; both converters and convert_to_ometiff (CLI: --mpp) accept an mpp= override for sources with none.
• Fix a downsample_plane bug where halving a single-channel "minisblack" plane swapped height/width from the second sub-level onward (dormant until now since the only existing caller squeezes to 2D first).
• Docs, changelog, and notebook updates reflecting the new suffixes.

Test plan

• tests/test_converter.py extended with coverage for SlideioImageConverter, SlideioTiledSource, and the downsample_plane fix.

🤖 Generated with Claude Code

[read-the-docs-community]

Documentation build overview

📚 spatialrefinery | 🛠️ Build #34661615 | 📁 Comparing c4847ae against latest (799472d)

  🔍 Preview build  

5 files changed · ± 5 modified

± Modified

• changelog.html
• index.html
• installation.html
• generated/spatialrefinery.convert_to_ometiff.html
• notebooks/convert_to_ometiff.html

[codecov]

Codecov Report

❌ Patch coverage is 96.47887% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 74.53%. Comparing base (799472d) to head (c4847ae).

Files with missing lines	Patch %	Lines
src/spatialrefinery/core/converter.py	96.47%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #15      +/-   ##
==========================================
+ Coverage   72.36%   74.53%   +2.16%     
==========================================
  Files          14       14              
  Lines        1516     1653     +137     
==========================================
+ Hits         1097     1232     +135     
- Misses        419      421       +2     

Files with missing lines	Coverage Δ
src/spatialrefinery/core/converter.py	90.20% <96.47%> (+4.54%)	⬆️

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