feat: add Vtable marker trait for CTask<V> type safety

Add unsafe trait Vtable as a bound on CTask<V> and CGameTask<V>,
preventing arbitrary types from being used as vtable parameters.

- *const c_void implements Vtable (the default/untyped case)
- #[vtable] proc macro auto-generates `impl Vtable for *const MyVTable`
- CTask<V: Vtable> and CGameTask<V: Vtable> enforce the bound

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

crates/openwa-core/src/task/base.rs

@@ -105,7 +105,7 @@ crate::define_addresses! {
 ///   0x1C: 0x563210 ProcessFrame
 #[derive(FieldRegistry)]
 #[repr(C)]
-pub struct CTask<V: 'static = *const core::ffi::c_void> {
+pub struct CTask<V: Vtable = *const core::ffi::c_void> {
     /// 0x00: Pointer to virtual method table
     pub vtable: V,
     /// 0x04: Parent task in the hierarchy
@@ -141,6 +141,18 @@ pub struct CTask<V: 'static = *const core::ffi::c_void> {
 
 const _: () = assert!(core::mem::size_of::<CTask>() == 0x30);
 
+/// Marker trait for types that can be used as vtable pointers in `CTask<V>`.
+///
+/// Implemented automatically by the `#[vtable]` proc macro for `*const MyVTable`.
+/// Also implemented for `*const c_void` (the default/untyped case).
+///
+/// # Safety
+/// Implementors must be pointer-sized types pointing to valid vtable data.
+pub unsafe trait Vtable: 'static {}
+
+// Default vtable type (untyped)
+unsafe impl Vtable for *const core::ffi::c_void {}
+
 /// Trait for all task types in the CTask hierarchy.
 ///
 /// Provides safe access to the underlying CTask fields regardless of
@@ -177,7 +189,7 @@ pub unsafe trait Task {
 }
 
 // Blanket impl for any CTask<V>
-unsafe impl<V: 'static> Task for CTask<V> {}
+unsafe impl<V: Vtable> Task for CTask<V> {}
 
 // ---------------------------------------------------------------------------
 // Shared-data entity registry

crates/openwa-core/src/task/game_task.rs

@@ -31,7 +31,7 @@ pub const CGAMETASK_SOUND_EMITTER_VT: u32 = SOUND_EMITTER_VTABLE;
 /// Additional vtable (12 methods at offsets 0x1C-0x48 in vtable)
 #[derive(FieldRegistry)]
 #[repr(C)]
-pub struct CGameTask<V: 'static = *const core::ffi::c_void> {
+pub struct CGameTask<V: super::base::Vtable = *const core::ffi::c_void> {
     /// 0x00-0x2F: Base CTask fields
     pub base: CTask<V>,
     /// 0x30-0x83: Subclass-specific data (84 bytes). Each CGameTask derivative

crates/openwa-core/src/task/mod.rs

@@ -14,7 +14,7 @@ pub mod turn_game;
 pub mod worm;
 
 pub use arrow::{CTaskArrow, CTaskArrowVTable};
-pub use base::{CTask, CTaskBfsIter, SharedDataIter, SharedDataNode, SharedDataTable, Task};
+pub use base::{CTask, CTaskBfsIter, SharedDataIter, SharedDataNode, SharedDataTable, Task, Vtable};
 pub use cloud::{CTaskCloud, CTaskCloudVTable};
 pub use filter::{CTaskFilter, CTaskFilterVTable};
 pub use fire::{CTaskFire, CTaskFireVTable};
@@ -29,7 +29,7 @@ pub use worm::{CTaskWorm, CTaskWormVTable};
 
 // Task trait impls — safe access to CTask base regardless of inheritance depth.
 // CTask<V> impl is in base.rs (blanket impl).
-unsafe impl<V: 'static> Task for CGameTask<V> {}
+unsafe impl<V: Vtable> Task for CGameTask<V> {}
 unsafe impl Task for CTaskTeam {}
 unsafe impl Task for CTaskTurnGame {}
 unsafe impl Task for CTaskFilter {}

crates/openwa-derive/src/lib.rs

@@ -311,6 +311,9 @@ fn vtable_impl(
 
         #va_items
 
+        // Mark *const ThisVtable as a valid vtable pointer type for CTask<V>.
+        unsafe impl openwa_core::task::Vtable for *const #struct_name {}
+
         /// Bind this vtable's known methods as wrapper methods on a class struct.
         ///
         /// Usage: `bind_VtableName!(ClassName, vtable_field_name);`