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-font/src/lib.rs

@@ -29,7 +29,6 @@ pub mod sprite;
 
 pub use atlas::Atlas;
 pub use backend::{Backend, OPTIONS as options};
-
 pub use codepoint_map::CodepointMap;
 pub use codepoint_resolver::CodepointResolver;
 pub use collection::Collection;
@@ -39,7 +38,6 @@ pub use face::Face;
 pub use glyph::Glyph;
 pub use library::Library;
 pub use metrics::Metrics;
-
 pub use shared_grid::SharedGrid;
 pub use shared_grid_set::SharedGridSet;
 pub use sprite::{Face as SpriteFace, Sprite};