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/opengl/frame.rs

@@ -1,9 +1,11 @@
 //! Wrapper for handling render frames (`opengl/Frame.zig`).
 use std::sync::Arc;
 
-use super::OpenGL;
-use super::render_pass::{Attachment, Options as RenderPassOptions, RenderPass};
-use super::target::Target;
+use super::{
+    OpenGL,
+    render_pass::{Attachment, Options as RenderPassOptions, RenderPass},
+    target::Target,
+};
 use crate::backend::Health;
 
 /// Options for beginning a frame.