chore(deps): replace static_assertions with native const assertions

## Summary `static_assertions v1.1.0` is used in several places across the kernel for compile-time checks. Since this is a nightly Rust project, most uses can be replaced with stable/nightly language features. ## Usage audit | Macro | Locations | Replacement | |---|---|---| | `const_assert_eq!` | `kernel/src/arch/riscv64/mem.rs`, `kernel/src/arch/riscv64/device/plic.rs`, `kernel/src/wasm/vm/vmcontext.rs`, `kernel/src/wasm/vm/instance.rs` | `const { assert_eq!(...) }` (stable since 1.57) | | `const_assert!` | `kernel/src/wasm/store/mod.rs` | `const { assert!(...) }` | | `assert_impl_all!` | `kernel/src/wasm/store/mod.rs` — verifies `StoreOpaque: Send + Sync` | Requires a small helper function with trait bounds (see below) | For `assert_impl_all!`, the idiomatic native replacement is: ```rust const fn _assert_send_sync<T: Send + Sync>() {} const _: () = _assert_send_sync::<StoreOpaque>(); ``` ## Action 1. Replace all `const_assert_eq!` / `const_assert!` uses with `const { assert_eq!(...) }` / `const { assert!(...) }`. 2. Replace `assert_impl_all!` with inline const-fn helpers. 3. Remove `static_assertions` from all `Cargo.toml` files. ## Impact Removes 1 external crate. Zero runtime impact.