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/metric_modifier.rs

@@ -3,10 +3,13 @@
 //! The font crate depends on this crate (not the other way around), so the
 //! modifier type used by the `adjust-*` config options lives here.
 
-use crate::cli_args::{ArgError, ConfigField};
-use crate::formatter::EntryFormatter;
 use std::fmt;
 
+use crate::{
+    cli_args::{ArgError, ConfigField},
+    formatter::EntryFormatter,
+};
+
 /// A modifier to apply to a metrics value. The modifier value represents
 /// a delta, so percent is a percentage to change, not a percentage of.
 /// For example, "20%" is 20% larger, not 20% of the value. Likewise,