refactor: apply clippy::unnecessary_map_or

[shulaoda]

Summary

• Replaces Option::map_or(false, |x| ..) with Option::is_some_and(..) and
  Option::map_or(true, |x| ..) with Option::is_none_or(..) across src/.
• One occurrence in src/comment.rs is further simplified to a direct
  Option equality check (orig.chars().nth(3) != Some('/')).
• Addresses clippy::unnecessary_map_or, run as a single-rule pass:
  cargo clippy -- -A clippy::all -W clippy::unnecessary_map_or.

[ytmimi]

Going to close until we decide on which clippy lints we want to enforce in the codebase.