Port multi-task unit tests from pipecat-subagents

Brings over 215 tests across 15 files covering the new
multi-task framework: BaseTask / PipelineTask bus lifecycle,
job RPC and job groups, the bus message hierarchy and serializers,
TaskBus + AsyncQueueBus + RedisBus + PgmqBus (with direct and
isolated backends), TaskRegistry, the BusBridgeProcessor, the
WebSocket proxy tasks, the LLMTask deferral logic, and the
PipelineRunner spawn-and-attach flow.

tests/test_bus_network.py

@@ -0,0 +1,35 @@
+#
+# Copyright (c) 2026, Daily
+#
+# SPDX-License-Identifier: BSD 2-Clause License
+#
+
+"""Tests for ``pipecat.bus.network`` lazy imports."""
+
+import unittest
+
+import pipecat.bus.network as network
+
+
+class TestNetworkPackageLazyImports(unittest.TestCase):
+    def test_pgmq_bus_lazy_import(self):
+        """``PgmqBus`` is resolved on first attribute access."""
+        from pipecat.bus.network.pgmq import PgmqBus as Direct
+
+        self.assertIs(network.PgmqBus, Direct)
+
+    def test_redis_bus_lazy_import(self):
+        """``RedisBus`` is resolved on first attribute access."""
+        from pipecat.bus.network.redis import RedisBus as Direct
+
+        self.assertIs(network.RedisBus, Direct)
+
+    def test_unknown_attribute_raises(self):
+        """Unknown attributes raise a clear ``AttributeError``."""
+        with self.assertRaises(AttributeError) as ctx:
+            network.NotARealBus  # noqa: B018
+        self.assertIn("NotARealBus", str(ctx.exception))
+
+
+if __name__ == "__main__":
+    unittest.main()