Clippy clean, and rustfmt and clippy part of the checks

cargo clippy --workspace --all-targets had 24 warnings; its own fixes took
most, the rest by hand: two type aliases for long types, a struct built
whole, a checked division, a doc comment's stray blank line. Its fix for
the stale-feed fold was wrong: `any` stops at the first feed it removes,
where the fold removed every one, so that is a loop instead.

A pre-commit hook in .githooks refuses unformatted Rust; clippy, being a
build, is in CLAUDE.md's checks with -D warnings.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

crates/feed/src/lib.rs

@@ -386,8 +386,11 @@ fn patreon_campaign(head: &[u8]) -> Option<String> {
     })
 }
 
+/// A campaign's name, and its shows as (id, title).
+type PatreonShows = (Option<String>, Vec<(String, String)>);
+
 /// A campaign's name and its shows as (id, title), from Patreon's JSON:API answer.
-fn parse_patreon_shows(json: &[u8]) -> Result<(Option<String>, Vec<(String, String)>)> {
+fn parse_patreon_shows(json: &[u8]) -> Result<PatreonShows> {
     let v: serde_json::Value = serde_json::from_slice(json).context("Patreon's answer is not JSON")?;
     // Missing is not the same as none. Read as no shows, the creator feed would be scanned as
     // a plain feed, claim every show's files, and leave the shows empty once the list returned.