Python: _ styled as a keyword in case[_]: int = 1 #242

Applies to the PyCaseWildcardPattern added in #236 (not on main yet).

When a snippet has no enclosing block, the pattern accepts any line that looks like a case clause. case[_]: int = 1 at the top level fits that shape, so its _ gets keyword styling even though Python reads the line as an annotated assignment to case[_].

Steps to reproduce

use Tempest\Highlight\Highlighter;

echo (new Highlighter())->parse('case[_]: int = 1', 'python');

Expected

_ stays plain. Python's ast parses the line as AnnAssign(target=Subscript(value=Name('case'), slice=Name('_'))).

Actual

case[<span class="hl-keyword">_</span>]: ...

Notes

• This only happens at a snippet's top level. Inside an if, def or any block other than match, the line is left alone.
• Top-level snippets are still accepted on purpose, because docs often show case _: without its match line. Telling the two apart would need something like "only = after the colon means an annotation", which a real case body such as case [x]: y = 1 breaks.