feat: make -t sort by modification time (GNU ls compat)

[catlee]

Problem

wls -trl (a very common GNU ls idiom) fails because in eza, -t is short for --time which selects which timestamp column to display and requires a value (modified, changed, accessed, created). When combined flags like -trl are parsed, r gets interpreted as the value for -t, which is invalid.

This is a known pain point when eza is aliased to ls — the most common way people use it. Since wish aliases ls to wls for all World users, GNU ls muscle memory should work.

Solution

Repurpose -t to mean "sort by modification time" (matching GNU ls behavior), and remove the -t short form from --time. The --time long form still works for selecting which time column to display, and the existing short flags for specific time fields (-m modified, -u accessed, -U created) are unaffected.

Changes

• Remove -t short form from the --time flag
• Add new -t/--sort-time flag (no value required, sorts by modification time)
• Error if both -t and --sort are given (conflicting sort options)
• Update help text and tests

GNU ls compatibility

GNU ls	Before (wls)	After (wls)
ls -t	❌ error (needs value)	✅ sort by mod time
ls -trl	❌ error (r not a valid time field)	✅ long, reversed, sorted by mod time
--time=accessed -l	✅ works	✅ still works

Breaking change

-t modified / -tmod no longer works as a short form of --time modified. Use --time modified or the dedicated short flags (-m, -u, -U) instead. This is an eza-ism that doesn't match GNU ls behavior, and since wls is aliased to ls, matching GNU conventions is more important.