feat: optionally hard-wrap inline pastes

[variablenix]

Summary

• add configurable hard wrapping for inline IRC paste text
• preserve URL-fetched content by default, with opt-in hard_wrap_urls
• document hard_wrap, hard_wrap_width, and hard_wrap_urls
• add word-wrap and paragraph-preservation tests

Validation

• go test ./...
• go vet ./...
• git diff --check