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-os/src/uri.rs

@@ -1,8 +1,7 @@
 //! URI parsing. Extends a faithful port of Zig's `std.Uri.parse` with the
 //! additional [`ParseOptions`] from `os/uri.zig`.
 
-use std::borrow::Cow;
-use std::fmt::Write as _;
+use std::{borrow::Cow, fmt::Write as _};
 
 #[derive(Debug, Clone, Copy, Default)]
 pub struct ParseOptions {