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>

CLAUDE.md

@@ -171,6 +171,8 @@ Patching that file by guessing an anchor string has failed repeatedly. Read the
 ## Tests
 
 ```sh
+cargo fmt --all --check   # rustfmt, as rustfmt.toml says; the pre-commit hook refuses a commit without it
+cargo clippy --workspace --all-targets -- -D warnings  # no warnings, ever
 cargo test                # ~80 tests: parsing, filters, retention, schedules, SQL, per-user state
 npx tsc -p .              # type-checks web/src
 node tests/page-smoke.js
@@ -194,6 +196,13 @@ session was stopped. So:
 * Builds and test binaries live under `target/`, a link to `/mnt/fast`; linking through
   `/mnt/user` (FUSE) once took the load to 248 on its own.
 
+The Rust is formatted by rustfmt (`rustfmt.toml`) and kept free of clippy's warnings. A clone
+turns on the hook once: `git config core.hooksPath .githooks`; and `git config blame.ignoreRevsFile
+.git-blame-ignore-revs` keeps blame past the commit that first formatted everything. A clippy
+suggestion is not always the same code: on adopting it, `fold(false, |any, id| remove(id) || any)`
+was offered as `any(...)`, which stops at the first and would have removed one feed of many. A lint
+that is wrong for a line gets `#[allow(clippy::...)]` there with a comment saying why.
+
 Things about the browser suite that have cost time:
 
 * It starts **its own daemon and database** under `/tmp/ipx-ui-test`, wiped once per run. Playwright