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/align.rs

@@ -106,7 +106,10 @@ impl Similarity {
         let det = self.a * self.a + self.b * self.b;
         let du = u - self.tx;
         let dv = v - self.ty;
-        ((self.a * du + self.b * dv) / det, (-self.b * du + self.a * dv) / det)
+        (
+            (self.a * du + self.b * dv) / det,
+            (-self.b * du + self.a * dv) / det,
+        )
     }
 }
 
@@ -253,10 +256,7 @@ mod tests {
         let (s, c) = (rot.sin(), rot.cos());
         let mut out = [(0.0, 0.0); 5];
         for (i, &(x, y)) in ARCFACE_TEMPLATE.iter().enumerate() {
-            out[i] = (
-                scale * (c * x - s * y) + dx,
-                scale * (s * x + c * y) + dy,
-            );
+            out[i] = (scale * (c * x - s * y) + dx, scale * (s * x + c * y) + dy);
         }
         out
     }