fix(plugin): fall back on Python AST recursion errors

[WenJing95]

Summary

Ran into this one late: a long enough Python expression makes ast.parse() throw RecursionError, even well under the 64 KiB preview limit. Nothing caught it, so rank-input generation just died instead of falling back to a source preview.

Changes

• Catch RecursionError with the other parse errors so it uses the existing fallback.
• Added regression tests with a real long expression.

Testing

Tests pass.

Risk and rollout

Small. Only previews that hit RecursionError behave differently, and they now use the fallback we already had.

Public disclosure review

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[mldangelo-oai]

Thank you for catching this and adding regression coverage with a real Python expression. I verified all three new cases on Python 3.12: they pass with this change and fail when the added RecursionError catch is removed.

The tests cover both preview entry points, the source and simple-outline fallbacks, and the byte limit. The CLI case also checks that the affected file stays in the rank input and processing continues to the next file. Reusing the existing fallback keeps this fix small and focused.

CI is green too, including all required platform checks, the portable source checks, and the full Python suite (1,223 passed, 8 skipped). Looks good to merge!