Mostly `cargo clippy --fix`: needless borrows, redundant field names,
match -> if let, io::Error::other, Option::filter/map, let chains, c""
literals. By hand: drop unused impl lifetimes, a type alias for the
font preload map, Iterator::find in next_buffer, contains_key, and
allow new_ret_no_self where constructors intentionally return the
boxed/generic wrapper type.
No functional change; tests and release build unchanged.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Desktop derived Hash over every field but PartialEq compared only the
name, violating the Hash/Eq contract the launcher's HashMap relies on
(clippy denies this by default, so `cargo clippy` failed to build).
Also skip directories and files without a .desktop extension (mimeinfo
cache, .directory files, ...) and stop unwrapping non-UTF-8 paths.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
