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/edit.rs

@@ -1,9 +1,8 @@
 //! Opening the config for editing (port of `config/edit.zig`).
 
+use std::{fs::OpenOptions, io, path::Path};
+
 use crate::file_load;
-use std::fs::OpenOptions;
-use std::io;
-use std::path::Path;
 
 /// The path to the configuration that should be opened for editing.
 ///