Adapt to Textual 0.87.1

The new textual release has some changes:

* We need to change how our tests 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 was a regression in how focusing a widget while the app is still
  starting up behaves. This has been fixed upstream in
  Textualize/textual#5284 but our snapshots
  will not pass until the fix makes it into a release.

Signed-off-by: Matt Wozniski <[email protected]>

Author: pablogsal

tests/conftest.py

@@ -5,7 +5,7 @@
 from packaging import version
 
 SNAPSHOT_MINIMUM_VERSIONS = {
-    "textual": "0.81",
+    "textual": "0.87.1",
     "pytest-textual-snapshot": "1.0",
 }
 

tests/unit/__snapshots__/test_tree_reporter/TestTUILooks.test_allocations_of_different_sizes.svg

@@ -140,7 +140,7 @@ async def run_before_wrapper(pilot) -> None:
 
 def render_widget(widget: Widget) -> str:
     output = StringIO()
-    rprint(widget.render(), file=output)
+    rprint(widget.renderable, file=output)
     return output.getvalue()