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/src/props_table.rs

@@ -1,8 +1,10 @@
 //! The generated Unicode property lookup table for Ghostty
 //! (`props_table.zig`). Generated by `build.rs`.
 
-use crate::lut::Tables;
-use crate::props::{GraphemeBreakNoControl, Properties};
+use crate::{
+    lut::Tables,
+    props::{GraphemeBreakNoControl, Properties},
+};
 
 mod generated {
     use super::{GraphemeBreakNoControl, Properties};