Bahex 0b2d1327d2
fix extern commands' extra description (#14996)
# Description

- Remove redundant fields from KnownExternal
- Command::extra_description and Command::search_terms using the
signature field

# User-Facing Changes

`extern` commands extra description is now shown in help text.

# Tests + Formatting

# After Submitting
2025-02-06 12:56:40 +01:00
..
2025-01-26 12:30:58 +08:00