Two-part fix for the CI break that followed the previous push.
Lint fix:
`crates/headroom-core/src/transforms/smart_crusher/analyzer.rs:779` used
`pairs.sort_by(|a, b| b.1.cmp(&a.1))`. Clippy 1.95 introduced
`unnecessary_sort_by` and prefers `sort_by_key(|b|
std::cmp::Reverse(b.1))` for the same desc-sort by a single field.
Replaced. Functionally identical (both stable sorts on the count field
descending; first-occurrence tie order preserved either way).
Drift fix:
The same lint passed locally on rust 1.92 / clippy 0.1.92 because the
dev box hadn't been updated since December. CI runners use
`dtolnay/rust-toolchain@stable` which always grabs the latest stable
(1.95 today), so any lint added between local's last update and CI's
runner image breaks the pre-push gate. Two ways to close this:
1. Pin a specific Rust version in `rust-toolchain.toml`.
2. Run `rustup update stable` before every push.
Option 1 is more robust — `rust-toolchain.toml` is auto-respected by
`cargo`, so any local check (or CI check using the same project) syncs
to the pinned version automatically. Pinned to `1.95.0`. Bump procedure
documented in the file: edit channel, `rustup update`, `make
ci-precheck`, fix any new lints, commit.
Verification:
- `rustup` synced the dev box to 1.95.0 on the next `cargo` invocation.
- `cargo clippy --workspace -- -D warnings` clean on 1.95.
- `make ci-precheck` green (388 rust + 185 python + commitlint).
