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-apprt-gtk/src/class/imgui_widget.rs

@@ -9,15 +9,15 @@
 //! cheaply in gtk-rs without a lot of class struct boilerplate, so subclasses
 //! install the two hooks with [`ImguiWidget::set_hooks`] instead.
 
-use std::cell::{Cell, RefCell};
-use std::time::{Duration, Instant};
+use std::{
+    cell::{Cell, RefCell},
+    time::{Duration, Instant},
+};
 
-use adw::prelude::*;
-use adw::subclass::prelude::*;
+use adw::{prelude::*, subclass::prelude::*};
 use dear_imgui_glow::GlowRenderer;
 use ghostty_inspector::imgui::{Context, MouseButton, Ui};
-use gtk::glib::translate::IntoGlib;
-use gtk::{gdk, glib};
+use gtk::{gdk, glib, glib::translate::IntoGlib};
 
 use crate::key;