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-terminal/src/render.rs

@@ -34,6 +34,13 @@
 //! waste, it is recommended that the caller drop and start with an
 //! empty render state every so often.
 
+use std::collections::HashSet;
+
+use ghostty_vt::{
+    color::{self, Palette, Rgb},
+    modes::Mode,
+};
+
 use crate::{
     cursor,
     highlight::Flattened,
@@ -46,11 +53,6 @@ use crate::{
     style::{Color, Style},
     terminal::{Dirty as TerminalDirty, Terminal},
 };
-use ghostty_vt::{
-    color::{self, Palette, Rgb},
-    modes::Mode,
-};
-use std::collections::HashSet;
 
 /// Contains the state required to render the screen. See the module docs.
 #[derive(Debug, Clone)]