fix: sort newest aliases newest first

[JSap0914]

Summary

• Map --sort=new and --sort=newest to the existing newest-first modified-time ordering.
• Map --sort=old and --sort=oldest to the existing oldest-first modified-time ordering.
• Add parser regressions for the explicit new/newest/old/oldest aliases.

Fixes #1772

Tests

• cargo fmt --all -- --check
• cargo test deduce_sort_field_new --lib (failed before the fix, passed after the fix via focused alias tests)
• cargo test deduce_sort_field_ --lib
• cargo test options::filter::tests --lib
• cargo test --test cli_tests cli_all_tests
• cargo test --test cli_tests cli_unix_tests
• cargo test --lib
• cargo check --all-targets
• Manual CLI QA with temp files using controlled mtimes: --sort=newest produced newest, middle, oldest; --sort=oldest produced oldest, middle, newest.

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