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-cli/build.rs

@@ -8,8 +8,10 @@
 //! The version can be overridden with `GHOSTTY_VERSION_STRING` (Zig:
 //! `-Dversion-string`), which must be a semantic version.
 
-use std::path::{Path, PathBuf};
-use std::process::Command;
+use std::{
+    path::{Path, PathBuf},
+    process::Command,
+};
 
 fn run(cmd: &str, args: &[&str], dir: &Path) -> Option<String> {
     let out = Command::new(cmd)