feat: Enhance plugin runtime with new component registry and workflow executor

- Introduced `ComponentRegistry` for managing plugin components with support for registration, enabling/disabling, and querying by type and plugin.
- Added `EventDispatcher` to handle event distribution to registered event handlers, supporting both blocking and non-blocking execution.
- Implemented `WorkflowExecutor` to manage a linear workflow execution across multiple stages, including command routing and error handling.
- Created `ManifestValidator` for validating plugin manifests against required fields and version compatibility.
- Updated `RPCClient` to use `MsgPackCodec` for message encoding.
- Enhanced `PluginRunner` to support lifecycle hooks for plugins, including `on_load` and `on_unload`.
- Added sys.path isolation to restrict plugin access to only necessary directories.

src/plugin_runtime/protocol/__init__.py

@@ -1 +1 @@
-# Protocol 层 - RPC 消息模型、编解码、错误码
+

src/plugin_runtime/protocol/codec.py

@@ -1,13 +1,7 @@
-"""MsgPack / JSON 编解码器
-
-提供统一的消息编解码接口，生产环境默认使用 MsgPack，
-开发调试模式可切换为 JSON（仅编解码切换，传输层不变）。
-"""
+"""MsgPack 编解码器"""
 
 from typing import Any
 
-import json
-
 import msgpack
 
 from .envelope import Envelope
@@ -30,7 +24,7 @@ class Codec:
 
 
 class MsgPackCodec(Codec):
-    """MsgPack 编解码器（生产默认）"""
+    """MsgPack 编解码器"""
 
     def encode(self, obj: dict[str, Any]) -> bytes:
         return msgpack.packb(obj, use_bin_type=True)
@@ -47,34 +41,3 @@ class MsgPackCodec(Codec):
     def decode_envelope(self, data: bytes) -> Envelope:
         raw = self.decode(data)
         return Envelope.model_validate(raw)
-
-
-class JsonCodec(Codec):
-    """JSON 编解码器（开发调试用）"""
-
-    def encode(self, obj: dict[str, Any]) -> bytes:
-        return json.dumps(obj, ensure_ascii=False).encode("utf-8")
-
-    def decode(self, data: bytes) -> dict[str, Any]:
-        result = json.loads(data.decode("utf-8"))
-        if not isinstance(result, dict):
-            raise ValueError(f"期望解码为 dict，实际为 {type(result)}")
-        return result
-
-    def encode_envelope(self, envelope: Envelope) -> bytes:
-        return self.encode(envelope.model_dump())
-
-    def decode_envelope(self, data: bytes) -> Envelope:
-        raw = self.decode(data)
-        return Envelope.model_validate(raw)
-
-
-def create_codec(use_json: bool = False) -> Codec:
-    """创建编解码器实例
-
-    Args:
-        use_json: 是否使用 JSON（开发模式）。默认使用 MsgPack。
-    """
-    if use_json:
-        return JsonCodec()
-    return MsgPackCodec()