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/host/capability_service.py

@@ -73,15 +73,7 @@ class CapabilityService:
                 reason,
             )
 
-        # 2. 限流校验
-        allowed, reason = self._policy.check_rate_limit(plugin_id)
-        if not allowed:
-            return envelope.make_error_response(
-                ErrorCode.E_BACKPRESSURE.value,
-                reason,
-            )
-
-        # 3. 查找实现
+        # 2. 查找实现
         impl = self._implementations.get(capability)
         if impl is None:
             return envelope.make_error_response(
@@ -89,7 +81,7 @@ class CapabilityService:
                 f"未注册的能力: {capability}",
             )
 
-        # 4. 执行
+        # 3. 执行
         try:
             result = await impl(plugin_id, capability, req.args)
             resp_payload = CapabilityResponsePayload(success=True, result=result)