refactor(pi): share session manager runtime registry

src/agents/pi-extensions/session-manager-runtime-registry.ts

@@ -0,0 +1,29 @@
+export function createSessionManagerRuntimeRegistry<TValue>() {
+  // Session-scoped runtime registry keyed by object identity.
+  // The SessionManager instance must stay stable across set/get calls.
+  const registry = new WeakMap<object, TValue>();
+
+  const set = (sessionManager: unknown, value: TValue | null): void => {
+    if (!sessionManager || typeof sessionManager !== "object") {
+      return;
+    }
+
+    const key = sessionManager;
+    if (value === null) {
+      registry.delete(key);
+      return;
+    }
+
+    registry.set(key, value);
+  };
+
+  const get = (sessionManager: unknown): TValue | null => {
+    if (!sessionManager || typeof sessionManager !== "object") {
+      return null;
+    }
+
+    return registry.get(sessionManager) ?? null;
+  };
+
+  return { set, get };
+}