fix: clear error on disjoint instance IDs in render_shapes/labels/points

[SAY-5]

Closes #603.

When a table annotates the element (region key matches) but no instance_id values overlap, the call crashed with a bare KeyError: None from deep inside upstream spatialdata's join path. The traceback gave no indication that the instance ID sets were disjoint.

Added an explicit disjoint check before join_spatialelement_table: when at least one table row claims to annotate the element yet the instance_key values share nothing with the element's index, raise a ValueError naming the table, element, instance key, and the fix. Regression test in test_render_shapes.py.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 88.88889% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 77.57%. Comparing base (7e6a607) to head (2e33801).

Files with missing lines	Patch %	Lines
src/spatialdata_plot/pl/render.py	88.88%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #661      +/-   ##
==========================================
+ Coverage   77.54%   77.57%   +0.02%     
==========================================
  Files          11       11              
  Lines        3572     3581       +9     
  Branches      838      840       +2     
==========================================
+ Hits         2770     2778       +8     
  Misses        480      480              
- Partials      322      323       +1     

Files with missing lines	Coverage Δ
src/spatialdata_plot/pl/render.py	87.36% <88.88%> (+0.01%)	⬆️

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[timtreis]

Claude tends to be overly verbose, please remove this comment

[timtreis]

This is also overly verbose, reduce to one-liner

[timtreis]

Hey @SAY-5, thanks for your contribution. Few issues with this PR:

Your new guard sits between the _obs.index.name = None workaround and the try/finally that restores it. If the guard raises, the sdata[table_name].obs.index.name is left mutated which is a problem.

Also, this fix only applies to shapes, the same behaviour can happen for labels and points, so we'd need the same fix there.

[timtreis]

Don't reimport inside the test

[timtreis]

Operate on sdata_filt instead of sdata here

[SAY-5]

Thanks for the review. Reworked in 95fc089:

• Moved the disjoint-instance-ID guard so it runs before the obs.index.name workaround in _render_shapes, so a failed check can never leave the index name half-restored.
• Extracted the check into a shared _check_instance_ids_overlap helper and applied it to _render_labels (vs the label IDs) and _render_points (vs the points index) as well, so the disjoint-IDs case raises the same clear ValueError instead of an opaque KeyError: None for all three render functions.
• Added regression tests on the disjoint-IDs path for shapes, labels, and points; ruff check/ruff format clean.

Also retitled the PR to reflect the wider scope.

[timtreis]

Hey @SAY-5, thanks for the update! I had also left some more comments in the code directly that aren't yet addressed, also, the branch has conflicts with main. Would be great if you could finalise the PR 👍 Thanks!

[SAY-5]

Rebased onto current main (resolved a conflict in tests/pl/test_render_labels.py by keeping both the new instance_id==0 background guard test from #660 and this PR's disjoint-instance-ID regression test). ruff check and ruff format pass; the full non-plot test suite for test_render_shapes/labels/points (78 tests, including the 3 regression tests added here) passes locally. Ready for another look.

[SAY-5]

Addressed the inline notes: trimmed the verbose comments to one line, dropped the redundant in-test shapely reimport, and switched the shapes guard to use sdata_filt[element].index. ruff check/format pass.

[SAY-5]

Switched the overlap check to operate on sdata_filt and dropped the verbose comments. Rebased on main so there are no conflicts. New regression tests pass locally.