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-font/src/fontconfig.rs

@@ -4,9 +4,11 @@
 //! All raw FFI is confined to this module.
 #![allow(unsafe_code)]
 
-use std::ffi::{CStr, CString, c_int};
-use std::ptr::{self, NonNull};
-use std::sync::Arc;
+use std::{
+    ffi::{CStr, CString, c_int},
+    ptr::{self, NonNull},
+    sync::Arc,
+};
 
 use fontconfig_sys as sys;
 use fontconfig_sys::constants as fc;