fix(lint): clear the clippy gate across examples and tests

80 findings, not the 14 the first run showed -- clippy stops at the first
failing compilation unit, so `--keep-going` is what makes the list complete.

60 were machine-applicable (`cargo clippy --fix`). The rest by hand:

* five descending `sort_by` -> `sort_by_key(Reverse(..))`
* `chunks_exact(4)` on both sides of four zips, so the compared items stay
  `[u8; 4]` rather than one array against one slice
* three `type` aliases for the census maps and the captured-quad tuple
* `&PathBuf` -> `&Path` in two disc tests
* two range loops; one of them keeps `#[allow(needless_range_loop)]` with the
  reason -- the index is into a map's value, which changes each iteration
* the module doc list in `invert_capture` re-indented to markdown's rules
* `blit`'s eight arguments get `#[allow(too_many_arguments)]`, not a struct

One dead `let off = b.len();` in a `ratc` test is dropped rather than renamed.
The sibling test at :162 is the one that asserts an offset; if this one was
meant to as well, that is a test change and not a lint fix.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

crates/sylpheed-formats/examples/dm_rows.rs

@@ -5,7 +5,7 @@ fn short(s: &str) -> String {
         .trim_start_matches("UnitName_UN_")
         .into()
 }
-fn g<'a>(o: &'a IdxdObject, k: &str) -> String {
+fn g(o: &IdxdObject, k: &str) -> String {
     o.get_f32(k)
         .map(|v| {
             if v == v.trunc() {