style: cargo fmt under rustfmt 1.9 and gate formatting in CI

The repo was formatted under an older stable; rustfmt 1.9 (Rust 1.95)
wraps signatures and call sites differently, so every touched file was
picking up unrelated formatting hunks. One mechanical pass, and a
'cargo fmt --check' step in the test workflow (same pinned 1.95.0
toolchain) so drift can't accumulate again.

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

.gitea/workflows/test.yml

@@ -46,7 +46,7 @@ jobs:
         uses: dtolnay/rust-toolchain@master
         with:
           toolchain: 1.95.0
-          components: clippy
+          components: clippy, rustfmt
 
       - name: Cache cargo build
         uses: Swatinem/rust-cache@v2
@@ -60,6 +60,9 @@ jobs:
             libasound2-dev libudev-dev pkg-config libx11-dev libxcursor-dev \
             libxrandr-dev libxi-dev libwayland-dev libxkbcommon-dev
 
+      - name: Format check
+        run: cargo fmt --check
+
       # SQLX_OFFLINE uses the checked-in `.sqlx/` query cache (no live DB),
       # same as the web-e2e workflow's server prebuild.
       - name: Clippy (deny warnings)