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/render_pass.rs

@@ -1,11 +1,11 @@
 //! Wrapper for handling render passes (`opengl/RenderPass.zig`).
-use super::gl::{
-    Attachment as GlAttachment, BufferTarget, FramebufferTarget, Gl, Primitive, RawBuffer,
+use super::{
+    gl::{Attachment as GlAttachment, BufferTarget, FramebufferTarget, Gl, Primitive, RawBuffer},
+    pipeline::Pipeline,
+    sampler::Sampler,
+    target::Target,
+    texture::Texture,
 };
-use super::pipeline::Pipeline;
-use super::sampler::Sampler;
-use super::target::Target;
-use super::texture::Texture;
 
 /// What a color attachment renders into.
 pub enum AttachmentTarget<'a> {