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-datastruct/src/blocking_queue.rs

@@ -1,9 +1,11 @@
 //! Blocking queue implementation aimed primarily for message passing
 //! between threads (`blocking_queue.zig`).
 
-use std::collections::VecDeque;
-use std::sync::{Condvar, Mutex, MutexGuard, PoisonError};
-use std::time::Duration;
+use std::{
+    collections::VecDeque,
+    sync::{Condvar, Mutex, MutexGuard, PoisonError},
+    time::Duration,
+};
 
 /// The type we use for queue size types.
 pub type Size = u32;
@@ -179,9 +181,9 @@ impl<T, const CAPACITY: usize> Drop for DrainIterator<'_, T, CAPACITY> {
 
 #[cfg(test)]
 mod tests {
+    use std::{sync::Arc, thread};
+
     use super::*;
-    use std::sync::Arc;
-    use std::thread;
 
     #[test]
     fn basic_push_and_pop() {

crates/ghostty-datastruct/src/lru.rs

@@ -4,8 +4,10 @@
 //! allocated entries; here the entries live in a slab and are linked by
 //! index.
 
-use std::collections::HashMap as StdHashMap;
-use std::hash::{BuildHasher, Hash, RandomState};
+use std::{
+    collections::HashMap as StdHashMap,
+    hash::{BuildHasher, Hash, RandomState},
+};
 
 /// Create a HashMap for a key type that can be automatically hashed.
 /// If you want finer-grained control, use [`HashMap`] directly.

crates/ghostty-datastruct/src/split_tree.rs

@@ -20,9 +20,10 @@
 //! parameters / `Allocator.Error`), the arena is replaced by a `Vec`, and the
 //! GObject boxed-type glue (`getGObjectType`) is left to the GTK crate.
 
-use half::f16;
 use std::fmt;
 
+use half::f16;
+
 /// The requirements on the view type stored in a [`SplitTree`].
 pub trait SplitTreeView: Clone {
     /// Return a label that is used for the debug view. If this returns