refactor: use k256 std feature instead of custom critical-section impl

Simpler approach - no custom code needed. Slightly larger WASM (+4K)
but cleaner codebase.

Author: OttoAllmendinger

packages/wasm-bip32/Cargo.lock

@@ -21,7 +21,7 @@ k256 = { version = "0.13", default-features = false, features = [
     "sha256",
     "alloc",
     "precomputed-tables",
-    "critical-section",
+    "std",
 ] }
 sha2 = { version = "0.10", default-features = false }
 ripemd = { version = "0.1", default-features = false }
@@ -30,8 +30,6 @@ bs58 = { version = "0.5", default-features = false, features = [
     "alloc",
 ] }
 getrandom = { version = "0.2", features = ["js"] }
-# Provide critical-section implementation for WASM (single-threaded, so no-op)
-critical-section = "1.2"
 
 [dev-dependencies]
 wasm-bindgen-test = "0.3"

packages/wasm-bip32/Cargo.toml

@@ -6,19 +6,3 @@ mod message;
 pub use bip32::WasmBIP32;
 pub use ecpair::WasmECPair;
 pub use error::WasmBip32Error;
-
-// Provide a no-op critical section implementation for single-threaded WASM
-use critical_section::RawRestoreState;
-
-struct SingleThreadedCs;
-critical_section::set_impl!(SingleThreadedCs);
-
-unsafe impl critical_section::Impl for SingleThreadedCs {
-    unsafe fn acquire() -> RawRestoreState {
-        // WASM is single-threaded, no actual locking needed
-    }
-
-    unsafe fn release(_restore_state: RawRestoreState) {
-        // WASM is single-threaded, no actual unlocking needed
-    }
-}