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-core/tests/e2e_term.rs

@@ -5,8 +5,10 @@
 
 mod common;
 use common::*;
-use ghostty_apprt::action::Action;
-use ghostty_apprt::structs::{Clipboard, SurfaceSize};
+use ghostty_apprt::{
+    action::Action,
+    structs::{Clipboard, SurfaceSize},
+};
 use ghostty_input::Key;
 use ghostty_vt::osc::ProgressState;