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_support/ucd.rs

@@ -17,9 +17,9 @@
     clippy::expect_used
 )]
 
+use std::{fs, path::Path};
+
 use crate::props::{GraphemeBreakNoControl as Gb, Properties};
-use std::fs;
-use std::path::Path;
 
 /// Highest codepoint known to the UCD (`uucode.config.max_code_point`).
 pub const MAX_CODE_POINT: u32 = 0x10FFFF;