Initial commit: Cyrene Plugins SDK + Plugin Manager

Extracted from Cyrene main repo (backend/pkg/plugins + backend/plugin-manager).
Contains SDK interfaces (Plugin/Tool/HostAPI), 13 built-in plugins,
ToolRegistry with call log ring buffer, and Plugin Manager REST API service.

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

cmd/plugin-manager/host_api.go

@@ -0,0 +1,47 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"log"
+	"net/http"
+
+	"git.yeij.top/AskaEth/Cyrene-Plugins/manager"
+	"git.yeij.top/AskaEth/Cyrene-Plugins/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
+}