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-renderer/src/state.rs

@@ -3,9 +3,7 @@
 use std::sync::{Arc, Mutex};
 
 use ghostty_input::Mods;
-use ghostty_terminal::point::Coordinate;
-use ghostty_terminal::size::CellCountInt;
-use ghostty_terminal::terminal::Terminal;
+use ghostty_terminal::{point::Coordinate, size::CellCountInt, terminal::Terminal};
 
 use crate::overlay::Feature as OverlayFeature;