feat(text): expose regex message argument #20

Summary

• Expose the configured regex text through the RegularExpression message argument.
• Preserve typed construction errors for invalid patterns.
• Cover substring and anchored behavior, messages, and rule codes.
• Update the source mirror and package README.

Closes #19.

Validation

• rg --files src test -g '*.pudu' | xargs pudu check
• pudu lint src test
• pudu fmt --check src test
• pudu test test — 19 suites, 171 assertions
• pudu build src/Main.pudu -o /tmp/pudu-lang-validator
• Compiled CLI --version smoke run
• Independent source and wiki review