style(cli): use div ceil for adaptive ABI alignment

Clippy rejects the hand-written round-up expression used to compute the callback-alignment offset in the Rust file-I/O projection. Use the equivalent div_ceil spelling so the ABI assertion remains clear and the root Rust targets pass with warnings denied.

Test Plan:

- cargo +nightly fmt --manifest-path rust/Cargo.toml --all -- --check

- git diff --check

- ulimit -v 41943040; CARGO_BUILD_JOBS=1 cargo clippy --manifest-path rust/Cargo.toml --all-targets -- -D warnings

rust/src/fileio_asyncio.rs

@@ -1104,9 +1104,8 @@ pub struct FIO_rust_zstd_compress_projection_t {
     pub adaptive_diagnostic: Option<FIO_rust_zstd_adaptive_diagnostic_fn>,
 }
 const _: () = {
-    let callback_offset = (14 * size_of::<usize>() + 5 * size_of::<c_int>() + size_of::<usize>()
-        - 1)
-        / size_of::<usize>()
+    let callback_offset = (14 * size_of::<usize>() + 5 * size_of::<c_int>())
+        .div_ceil(size_of::<usize>())
         * size_of::<usize>();
     assert!(
         std::mem::offset_of!(FIO_rust_zstd_compress_projection_t, adaptive_mode)