fix: exclude io::Write impl on wasm32v1-none to avoid core_io_borrowed_buf

When the std feature is unified to true by workspace feature resolution but
the target is wasm32v1-none, lib.rs forces no_std mode and aliases core as
std. In that configuration 'use std::io' becomes 'use core::io', which is
gated behind the unstable core_io_borrowed_buf feature (tracking issue #117693,
not stable in Rust 1.88).

Gate both the 'use std::io' import and the io::Write impl behind
not(all(target_arch = "wasm32", target_os = "none")) to prevent this.
The io::Write impl is irrelevant on no_std wasm targets anyway.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/arrayvec.rs

@@ -11,7 +11,11 @@ use std::borrow::{Borrow, BorrowMut};
 use std::hash::{Hash, Hasher};
 use std::fmt;
 
-#[cfg(feature="std")]
+// Exclude wasm32v1-none: even when std feature is unified to true by workspace
+// feature resolution, this target forces no_std (see lib.rs cfg_attr). In no_std
+// mode `std` is aliased to `core`, and `core::io` is gated behind the unstable
+// `core_io_borrowed_buf` feature (not stable in Rust 1.88, tracking: #117693).
+#[cfg(all(feature = "std", not(all(target_arch = "wasm32", target_os = "none"))))]
 use std::io;
 
 use std::mem::ManuallyDrop;
@@ -1252,7 +1256,7 @@ impl<T, const CAP: usize> Ord for ArrayVec<T, CAP> where T: Ord {
     }
 }
 
-#[cfg(feature="std")]
+#[cfg(all(feature = "std", not(all(target_arch = "wasm32", target_os = "none"))))]
 /// `Write` appends written data to the end of the vector.
 ///
 /// Requires `features="std"`.