feat: Phase 3 插件与工具系统 — Plugin SDK + Plugin Manager + 13内置插件 (40文件, 3293行)

- Plugin SDK: Plugin/Tool/ComplexTool/HostAPI 标准化接口
- Plugin Manager: 插件生命周期管理 (Install/Enable/Disable/Uninstall/Reload)
- Tool Registry: 聚合工具注册表 (Register/Execute/Dispatch)
- 13 个内置插件: 将原有硬编码工具迁移为标准插件格式
- REST API: 11 个端点 (net/http, 零外部依赖)
- ai-core 集成: PluginManagerClient 替代本地工具调用
- plugin.json 元数据: 每个插件含完整 author/version/category/permissions

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

backend/plugin-manager/cmd/host_api.go

@@ -0,0 +1,51 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"log"
+	"net/http"
+
+	"github.com/yourname/cyrene-ai/plugin-manager/internal/manager"
+	"github.com/yourname/cyrene-ai/plugin-manager/internal/sdk"
+)
+
+type hostAPI struct {
+	registry *manager.ToolRegistry
+}
+
+func newHostAPI(registry *manager.ToolRegistry) *hostAPI {
+	return &hostAPI{registry: registry}
+}
+
+func (h *hostAPI) CallLLM(_ context.Context, _ []sdk.LLMMessage) (*sdk.LLMResponse, error) {
+	return nil, fmt.Errorf("LLM call not available in plugin host")
+}
+
+func (h *hostAPI) SearchMemory(_ context.Context, _, _ string, _ int) ([]sdk.MemoryEntry, error) {
+	return nil, fmt.Errorf("memory search not available in plugin host")
+}
+
+func (h *hostAPI) StoreMemory(_ context.Context, _ sdk.MemoryEntry) error {
+	return fmt.Errorf("memory store not available in plugin host")
+}
+
+func (h *hostAPI) Logger() sdk.Logger {
+	return log.Default()
+}
+
+func (h *hostAPI) GetConfig(key string) (string, error) {
+	return "", fmt.Errorf("config key not found: %s", key)
+}
+
+func (h *hostAPI) SetConfig(_, _ string) error {
+	return nil
+}
+
+func (h *hostAPI) PublishEvent(_ context.Context, _ map[string]interface{}) error {
+	return nil
+}
+
+func (h *hostAPI) HTTPClient() *http.Client {
+	return http.DefaultClient
+}