Rename BaseTask → BaseWorker and reserve "task" for asyncio

Replaces every "task" identifier that referred to the BaseTask
abstraction with "worker". Asyncio task plumbing (asyncio.Task,
BaseTaskManager, TaskManager, create_task, cancel_task, etc.) stays
untouched. Highlights:

- Classes: BaseTask → BaseWorker, PipelineTask → PipelineWorker,
  LLMTask → LLMWorker, LLMContextTask → LLMContextWorker, TaskBus →
  WorkerBus, TaskRegistry → WorkerRegistry, TaskActivationArgs →
  WorkerActivationArgs, TaskReadyData → WorkerReadyData,
  TaskRegistryEntry → WorkerRegistryEntry, TaskObserver →
  WorkerObserver, all Bus*TaskMessage → Bus*WorkerMessage,
  BusAddTaskMessage.task field → worker, BusWorkerRegistryMessage.tasks
  field → workers.
- Methods/decorators: activate_task → activate_worker, deactivate_task
  → deactivate_worker, add_task → add_worker, watch_task →
  watch_worker, @task_ready → @worker_ready, setup_pipeline_task hook
  → setup_pipeline_worker.
- Params/fields: FrameProcessorSetup.pipeline_task and
  FunctionCallParams.pipeline_task → pipeline_worker. Parameter names
  like task_name → worker_name; spawn/run accept worker:.
- Files: pipeline/base_task.py → base_worker.py, pipeline/task.py →
  worker.py (plus a re-export shim at pipeline/task.py),
  task_observer.py → worker_observer.py, task_ready_decorator.py →
  worker_ready_decorator.py, pipecat.tasks → pipecat.workers,
  llm_task.py → llm_worker.py, llm_context_task.py →
  llm_context_worker.py, examples/multi-task → examples/multi-worker.

Back-compat:
- PipelineTask kept as a deprecated subclass of PipelineWorker that
  warns on construction.
- pipecat.pipeline.task re-exports PipelineWorker/PipelineTask/etc. so
  existing user imports keep working.
- FrameProcessor.pipeline_task kept as a deprecated property that
  forwards to pipeline_worker.

Local variables in examples that hold a worker (task = PipelineTask(...))
are renamed to worker = PipelineWorker(...). Asyncio-task locals
(runner_task, etc.) are preserved.

examples/multi-worker/code-assistant/code_worker.py

@@ -0,0 +1,118 @@
+#
+# Copyright (c) 2026, Daily
+#
+# SPDX-License-Identifier: BSD 2-Clause License
+#
+
+"""Code worker that explores a codebase using Claude Agent SDK."""
+
+import asyncio
+
+from loguru import logger
+
+from pipecat.bus import BusJobRequestMessage
+from pipecat.pipeline.base_worker import BaseWorker
+from pipecat.pipeline.job_context import JobStatus
+
+try:
+    from claude_agent_sdk import ClaudeAgentOptions, ClaudeSDKClient
+except ModuleNotFoundError as e:
+    logger.error(f"Exception: {e}")
+    logger.error("In order to use CodeWorker, you need to `pip install claude-agent-sdk`.")
+    raise Exception(f"Missing module: {e}")
+
+
+class CodeWorker(BaseWorker):
+    """Bus-only worker that answers code questions using Claude Agent SDK.
+
+    Maintains a persistent Claude SDK session so follow-up questions
+    share context. Questions are queued and processed sequentially. The
+    worker has no Pipecat pipeline — it consumes job requests from the
+    bus and replies with job responses.
+    """
+
+    def __init__(self, name: str, *, project_path: str):
+        """Initialize the CodeWorker.
+
+        Args:
+            name: Unique worker name.
+            project_path: Filesystem path the Claude SDK should explore.
+        """
+        super().__init__(name)
+
+        self._project_path = project_path
+        self._queue: asyncio.Queue = asyncio.Queue()
+        self._worker_task: asyncio.Task | None = None
+
+        self._claude_options = ClaudeAgentOptions(
+            permission_mode="bypassPermissions",
+            system_prompt=(
+                f"You are a code assistant. The project is at: {self._project_path}\n\n"
+                "Answer the user's question by exploring the codebase. Use Read to "
+                "view files, Glob to find files by pattern, and Bash to run commands "
+                "like grep or find. Be thorough but concise in your answer. "
+                "Focus on what the user asked. Respond with a clear, spoken-friendly "
+                "summary (no markdown, no bullet points, no code blocks)."
+            ),
+            allowed_tools=["Read", "Bash", "Glob", "Grep"],
+            model="sonnet",
+            max_turns=10,
+        )
+
+    async def start(self) -> None:
+        """Launch the Claude SDK worker loop alongside the standard worker start."""
+        await super().start()
+        self._worker_task = self.create_task(self._worker_loop(), "worker")
+
+    async def stop(self) -> None:
+        """Cancel the worker loop before tearing down the worker."""
+        if self._worker_task:
+            await self.cancel_task(self._worker_task)
+            self._worker_task = None
+        await super().stop()
+
+    async def on_job_request(self, message: BusJobRequestMessage) -> None:
+        """Enqueue an incoming job for the worker loop."""
+        await super().on_job_request(message)
+        logger.info(f"Worker '{self.name}': queued '{message.payload['question']}'")
+        self._queue.put_nowait(message)
+
+    async def _worker_loop(self):
+        client = ClaudeSDKClient(options=self._claude_options)
+        try:
+            await client.connect()
+        except Exception as e:
+            logger.error(f"Worker '{self.name}': failed to start Claude SDK: {e}")
+            return
+
+        try:
+            while True:
+                message = await self._queue.get()
+                question = message.payload["question"]
+                logger.info(f"Worker '{self.name}': researching '{question}'")
+
+                try:
+                    answer = ""
+                    await client.query(prompt=question)
+                    async for msg in client.receive_response():
+                        if type(msg).__name__ == "AssistantMessage":
+                            for block in msg.content:
+                                if type(block).__name__ == "TextBlock":
+                                    answer += block.text
+
+                    logger.info(f"Worker '{self.name}': completed ({len(answer)} chars)")
+                    await self.send_job_response(message.job_id, {"answer": answer})
+
+                except Exception as e:
+                    logger.error(f"Worker '{self.name}': error: {e}")
+                    await self.send_job_response(
+                        message.job_id, {"error": str(e)}, status=JobStatus.ERROR
+                    )
+        finally:
+            # Bypass `async with ClaudeSDKClient` and call disconnect()
+            # ourselves: __aexit__ → Query.close() → _read_task.wait() uses
+            # `with suppress(asyncio.CancelledError)`, which would swallow the
+            # outer task's cancellation. By the time this finally runs, our
+            # CancelledError has already been raised once, so _must_cancel is
+            # cleared and disconnect()'s awaits proceed normally.
+            await client.disconnect()