fix: expand punctuation realization aliases

[aryamantodkar]

Summary

• normalize repeated whitespace and case before punctuation parsing
• support common aliases for stops, quotes, delimiters, ellipses, symbols, and en/em dashes
• preserve complete-span rejection for unknown words and corpus silence tokens
• document punctuation coverage and add regression tests

Validation

• cargo test --manifest-path rust/Cargo.toml punctuation

This PR is stacked on #44.