Escape triple quotes in generated Python docstrings

[cestercian]

WIT /// documentation that contains """ was copied verbatim into generated Python """...""" docstrings, which is a SyntaxError (python -m py_compile fails).

Fixes #194

Summary

Generated Python bindings are now valid even when WIT docs include """ (and when they include both """ and '''). Documentation text is preserved.

Changes

• Update docstring() in src/summary.rs to pick a triple-quote delimiter that does not appear in the docs. If both """ and ''' are present, escape """ as \"\"\" and wrap with """.
• Add a bindings regression test using the issue WIT (plus a function whose docs contain both quote styles). The test generates stubs, ast.parses the output (so invalid Python fails), and asserts the documentation text is still present.

Testing

• cargo fmt --all -- --check
• cargo clippy --all-targets --tests -- -D warnings
• cargo test --test bindings docstring_triple_quotes_are_valid_python — passed

[dicej]

Thanks!