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-build-data/src/lib.rs

@@ -8,9 +8,7 @@
 #![cfg_attr(test, allow(clippy::expect_used))]
 
 use ghostty_cli::Action;
-use ghostty_config::cli_args::FieldKind;
-use ghostty_config::config::Config;
-use ghostty_config::macros::ConfigStruct;
+use ghostty_config::{cli_args::FieldKind, config::Config, macros::ConfigStruct};
 
 pub mod bash;
 pub mod fish;