feat(mcp): Top5#3 对齐 MCP Go SDK——协议版本协商 + list_changed 差量刷新 + keepalive + Streamable HTTP

- 协议版本协商：initialize 先发最高版本(2025-11-25)并声明能力集合，遇
  UnsupportedProtocolVersionError(-32022)/服务器不支持版本 → negotiateMutuallySupportedVersion
  求出双方最高共同版本降级重试(最多2次)；无共同版本→ErrUnsupportedProtocolVersion。
  协商结果记 negotiatedVersion，HTTP 传输回填 Mcp-Protocol-Version 头。
- tools/list_changed 订阅：capabilities 声明 tools.listChanged:true；传输读无 id 帧路由到
  handleServerNotification；refreshPending 原子旗标合并突发 + 新 goroutine 调 onToolListChanged
  (避免 stdio lineRPC 重入自锁)；Registry 真差量刷新(重新 DiscoverTools→移除消失/注册新增，
  跳过同名冲突保外来工具)。
- keepalive：WithKeepAlive(interval,failures) 起 goroutine 定时 Call(ping)，连续失败≥阈值关
  session(默认3,可配)；服务器不支持 ping(-32601)停 keepalive 不误关；ctx+Close 取消不泄漏。
- Streamable HTTP 传输：newTransport 支持 TransportType=http|streamable(保留 stdio/SSE 推断，
  空值走旧逻辑不破坏)；Call POST+Accept json/event-stream 响应可单 JSON 或 SSE 流找匹配 id；
  Mcp-Session-Id 会话 + 独立 GET SSE 流收 server 通知；config 读 MCP_TRANSPORT。
- schema 缓存判定不做：客户端透传 map[string]any 无重复编译，SDK SchemaCache 是服务端
  按 Go 类型反射场景，客户端无对应。

go build/vet/test 全绿(count=2 无 flaky) + windows/darwin 交叉编译。

internal/capability/mcp/registry_test.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"errors"
 	"testing"
+	"time"
 
 	"git.yeij.top/AskaEth/Cyrene_v2/internal/capability/registry"
 )
@@ -107,6 +108,58 @@ func TestRegistry_Unregister_Idempotent(t *testing.T) {
 	}
 }
 
+func TestRegistry_ToolListChangedRefreshes(t *testing.T) {
+	t.Parallel()
+	ft := &fakeTransport{tools: sampleTools()}
+	reg := registry.New()
+	r := NewRegistry(reg, MCPConfig{Name: "calc", Command: "x"}, WithTransport(ft))
+	if err := r.Register(context.Background()); err != nil {
+		t.Fatalf("Register: %v", err)
+	}
+	// The server's tool list changes: sub is dropped, mul appears.
+	ft.setTools([]ToolInfo{
+		{Name: "add", Description: "Adds numbers", InputSchema: map[string]any{"type": "object"}},
+		{Name: "mul", Description: "Multiplies numbers", InputSchema: map[string]any{"type": "object"}},
+	})
+	ft.notifyServer(notificationToolsListChanged)
+
+	waitFor(t, time.Second, func() bool {
+		_, err := reg.Get("mul")
+		return err == nil
+	})
+	if _, err := reg.Get("add"); err != nil {
+		t.Fatalf("Get(add) after refresh = %v, want present", err)
+	}
+	if _, err := reg.Get("sub"); !errors.Is(err, registry.ErrNotFound) {
+		t.Fatalf("Get(sub) after refresh = %v, want ErrNotFound", err)
+	}
+}
+
+func TestRegistry_ToolListChangedPreservesForeignTools(t *testing.T) {
+	t.Parallel()
+	ft := &fakeTransport{tools: sampleTools()}
+	reg := registry.New()
+	_ = reg.RegisterTool(&testTool{name: "add"}) // a foreign 'add' before refresh
+	r := NewRegistry(reg, MCPConfig{Name: "calc", Command: "x"}, WithTransport(ft))
+	if err := r.Register(context.Background()); err != nil {
+		// 'add' collides with the foreign tool; Register must surface the dup.
+		if !errors.Is(err, registry.ErrDuplicate) {
+			t.Fatalf("Register error = %v, want registry.ErrDuplicate", err)
+		}
+	}
+	// After the collision, sub is registered, 'add' stays foreign.
+	ft.setTools([]ToolInfo{{Name: "sub", Description: "Subtracts", InputSchema: map[string]any{}}})
+	ft.notifyServer(notificationToolsListChanged)
+	waitFor(t, time.Second, func() bool {
+		_, err := reg.Get("sub")
+		return err == nil
+	})
+	// The foreign 'add' must be preserved even though it is not in the server list.
+	if _, err := reg.Get("add"); err != nil {
+		t.Fatalf("Get(add) after refresh = %v, want foreign tool preserved", err)
+	}
+}
+
 // testTool is a minimal sdk.Tool used to pre-register a colliding name.
 type testTool struct {
 	name string