feat(kernel): add SpawnThread, CreateProcess, and Kill syscalls

crates/domain/src/endpoint/wait_queue.rs

@@ -29,6 +29,17 @@ impl WaitQueue {
         thread
     }
 
+    pub fn remove_thread(&mut self, thread: ThreadId) -> bool {
+        for slot in &mut self.entries {
+            if *slot == Some(thread) {
+                *slot = None;
+                self.count -= 1;
+                return true;
+            }
+        }
+        false
+    }
+
     pub fn is_empty(&self) -> bool {
         self.count == 0
     }