feat: add model and turn control commands

src/channels/shared/session-binding-lock.mjs

@@ -0,0 +1,40 @@
+const bindingLocks = new WeakMap();
+
+function stateLocks(state) {
+  let locks = bindingLocks.get(state);
+  if (!locks) {
+    locks = new Map();
+    bindingLocks.set(state, locks);
+  }
+  return locks;
+}
+
+/**
+ * Serialize the short Session binding transaction for one conversation.
+ * The caller must keep long-running Session work, such as ask(), outside.
+ */
+export async function withSessionBindingLock(state, key, operation) {
+  const stateType = typeof state;
+  if ((stateType !== 'object' && stateType !== 'function') || state === null) {
+    throw new TypeError('state is required');
+  }
+  if (typeof key !== 'string' || !key) throw new TypeError('conversation key is required');
+  if (typeof operation !== 'function') throw new TypeError('operation is required');
+
+  const locks = stateLocks(state);
+  const previous = locks.get(key) ?? Promise.resolve();
+  let release;
+  const current = new Promise((resolve) => { release = resolve; });
+  locks.set(key, current);
+
+  await previous;
+  try {
+    return await operation();
+  } finally {
+    release();
+    if (locks.get(key) === current) {
+      locks.delete(key);
+      if (locks.size === 0) bindingLocks.delete(state);
+    }
+  }
+}