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-unicode/build.rs

@@ -17,10 +17,7 @@ mod props;
 #[path = "build_support/ucd.rs"]
 mod ucd;
 
-use std::env;
-use std::fmt::Write as _;
-use std::fs;
-use std::path::PathBuf;
+use std::{env, fmt::Write as _, fs, path::PathBuf};
 
 fn main() {
     let manifest = PathBuf::from(env::var_os("CARGO_MANIFEST_DIR").unwrap());