Run the formatter over the face branch before it reaches CI

The merge of the SCRFD/MobileFaceNet work brought 69 rustfmt diffs across
dr-catalog, dr-face and dr-ui with it, so `cargo fmt --all -- --check` fails
on master and the Desktop job stops at its Format step — before clippy, the
tests or the release build have run at all. That makes the whole desktop
half of CI blind: a real compile error behind this would look exactly the
same from the outside. There was nothing behind it, as it turns out — with
the formatting fixed, clippy, the test suite and the release build all pass.

Every .rs hunk is `cargo fmt --all` on the pinned 1.92.0 toolchain, not a
hand edit, but it is worth being precise about what that moved, because it
is more than whitespace. Besides reflowing signatures and call chains,
rustfmt reordered the `pub mod` and `pub use` items in dr-face/src/lib.rs so
the `#[cfg(feature = "inference")]` entries sort in place, added the trailing
semicolon inside `let ... else { return }` bodies in identity_ui.rs, wrapped
a bare closure body in braces in cluster.rs, adjusted trailing commas, and
dropped a stray blank line at the end of identity_ui.rs. All of it is
semantically inert; none of it changes behaviour.

docs/traceability.md rides along because it has to. The matrix records each
TRACES tag by line number, and reflowing develop.rs, lib.rs, faces.rs,
identity.rs and identity_ui.rs moved them — FR-CAT-8, FR-CAT-9, FR-CULL-10,
FR-DEV-3, FR-DEV-3a and FR-DEV-3c all shift by a line or two. The matrix was
verified up to date on d777f7f before this commit, so this is drift these
formatting changes introduced, not pre-existing staleness being swept up.
Leaving it for a follow-up commit would hand traceability-check.yml a
failure caused entirely by a whitespace change.

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

core/dr-face/src/cluster.rs

@@ -75,11 +75,7 @@ pub struct Cluster {
 /// probability between two groups. Deterministic: the same input yields the
 /// same clusters, because the merge order is by score with the index pair as
 /// the tiebreak.
-pub fn cluster(
-    faces: &[Candidate],
-    cal: &Calibration,
-    min_probability: f32,
-) -> Vec<Cluster> {
+pub fn cluster(faces: &[Candidate], cal: &Calibration, min_probability: f32) -> Vec<Cluster> {
     if faces.is_empty() {
         return Vec::new();
     }
@@ -150,7 +146,12 @@ pub fn cluster(
         })
         .collect();
     // Largest first: the People view shows the best-evidenced groups at the top.
-    out.sort_by(|x, y| y.members.len().cmp(&x.members.len()).then(x.members[0].cmp(&y.members[0])));
+    out.sort_by(|x, y| {
+        y.members
+            .len()
+            .cmp(&x.members.len())
+            .then(x.members[0].cmp(&y.members[0]))
+    });
     out
 }