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-os/src/pipe.rs

@@ -1,5 +1,4 @@
-use std::io;
-use std::os::fd::OwnedFd;
+use std::{io, os::fd::OwnedFd};
 
 /// pipe() for POSIX. Sets CLOEXEC on the file descriptors.
 /// Returns `(read, write)`.
@@ -9,9 +8,10 @@ pub fn pipe() -> io::Result<(OwnedFd, OwnedFd)> {
 
 #[cfg(test)]
 mod tests {
-    use super::*;
     use std::io::{Read, Write};
 
+    use super::*;
+
     #[test]
     fn pipe_roundtrip_cloexec() {
         let (r, w) = pipe().unwrap();