style: apply nightly rustfmt import grouping across the workspace

rustfmt.toml sets group_imports, imports_granularity and imports_layout,
which are nightly-only; agents formatted with stable rustfmt, which
ignored them. This is a formatting-only pass with `cargo +nightly fmt`.

Test Plan:
- cargo clippy --workspace --all-targets -- -D warnings
- cargo test --workspace

crates/ghostty-input/src/lib.rs

@@ -21,6 +21,8 @@ pub use key_mods::{Mods, RemapSet as KeyRemapSet};
 pub use keyboard::Layout as KeyboardLayout;
 pub use link::Link;
 pub use mouse::{
-    Button as MouseButton, ButtonState as MouseButtonState, PressureStage as MousePressureStage,
+    Button as MouseButton,
+    ButtonState as MouseButtonState,
+    PressureStage as MousePressureStage,
     ScrollMods,
 };