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/screen/tests/p1.rs

@@ -1,6 +1,7 @@
-use super::*;
 use ghostty_vt::sgr::Attribute as A;
 
+use super::*;
+
 #[test]
 fn screen_read_and_write() {
     let mut s = init(80, 24, 1000);

crates/ghostty-terminal/src/screen/tests/p2.rs

@@ -1,6 +1,7 @@
-use super::*;
 use ghostty_vt::{color::Rgb, sgr::Attribute as A};
 
+use super::*;
+
 fn bg155() -> A<'static> {
     A::DirectColorBg(Rgb { r: 155, g: 0, b: 0 })
 }

crates/ghostty-terminal/src/screen/tests/p3.rs

@@ -1,6 +1,8 @@
 use super::*;
-use crate::page::Wide;
-use crate::screen::{PromptKind, SemanticContentSet};
+use crate::{
+    page::Wide,
+    screen::{PromptKind, SemanticContentSet},
+};
 
 fn cell_at(s: &Screen, pt: Point) -> Cell {
     s.pages.get_cell(pt).unwrap()

crates/ghostty-terminal/src/screen/tests/p5.rs

@@ -1,8 +1,7 @@
+use ghostty_vt::{color::Rgb, sgr::Attribute as A};
+
 use super::*;
-use crate::page::STD_CAPACITY;
-use crate::style::Color;
-use ghostty_vt::color::Rgb;
-use ghostty_vt::sgr::Attribute as A;
+use crate::{page::STD_CAPACITY, style::Color};
 
 fn sel_str(s: &Screen, sel: Selection, trim: bool) -> String {
     s.selection_string(SelectionString { sel, trim })