Adapt to textual 0.88.0

[pablogsal]

The new textual release has some changes:

• There are some changes that we need to do to get the rendered version
  of some textual objects as now render() returns RichVisual instances
• Textual has a new theme so we need to regenerate our snapshots.
• There is something going on with horizontal scroll bars. We have
  opened Horizontal scroll bar disappeared in 0.87.1 Textualize/textual#5284 but looks
  like this may be expected.

Issue number of the reported bug or feature request: #

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[pablogsal]

Note that Textualize/textual#5284 may still be a bug

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.87%. Comparing base (beea5cd) to head (46248f0).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #698      +/-   ##
==========================================
- Coverage   92.93%   92.87%   -0.07%     
==========================================
  Files          95       95              
  Lines       11655    11655              
  Branches      406      406              
==========================================
- Hits        10832    10824       -8     
- Misses        823      831       +8     

Flag	Coverage Δ
cpp	92.87% <100.00%> (-0.07%)	⬇️
python_and_cython	92.87% <100.00%> (-0.07%)	⬇️

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Copilot reviewed 23 out of 23 changed files in this pull request and generated no suggestions.

Comments skipped due to low confidence (1)

tests/unit/test_tui_reporter.py:144

• Ensure that the change from widget.render() to widget.renderable is covered by tests to verify the behavior remains correct.

rprint(widget.renderable, file=output)

[godlygeek]

We should update this to whatever version their next release is (either 0.88.0 or 0.87.2), since we know these tests don't pass with 0.87.1 (they need a release that contains Textualize/textual#5296 to pass)

[godlygeek]

This looks good to land as soon as Textual cuts a release that contains Textualize/textual#5296

Once they do, we should bump our SNAPSHOT_MINIMUM_VERSIONS to match their new version number, and then this PR should pass and we can rebase the others that have gotten blocked behind the failing CI.