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-config/src/command.rs

@@ -1,9 +1,12 @@
 //! A command to execute (port of `config/command.zig`).
 
-use crate::cli_args::{ArgError, ConfigField};
-use crate::formatter::EntryFormatter;
 use std::fmt;
 
+use crate::{
+    cli_args::{ArgError, ConfigField},
+    formatter::EntryFormatter,
+};
+
 /// A command to execute (argv0 and args).
 ///
 /// A command is specified as a simple string such as "nvim a b c".