refactor(go): keep protocol realtime snapshots lightweight

docs/architecture/production-data-plane-inventory.md

@@ -82,7 +82,7 @@ Redis 使用 DB 50，定位为实时缓存，不作为历史事实来源。
 | Key 族 | 用途 |
 | --- | --- |
 | `vehicle:latest:{vehicleKey}` | 跨协议合并后的最新核心字段快照，不重复保存完整 parsed |
-| `vehicle:latest:{vehicleKey}:{protocol}` | 单协议最新快照 |
+| `vehicle:latest:{vehicleKey}:{protocol}` | 单协议最新轻量快照，保留核心 fields 和时间信息，不重复保存完整 parsed |
 | `vehicle:realtime-raw:{protocol}:{vehicleKey}` | 单协议最新完整 parsed 状态，是实时完整协议字段的唯一 Redis 副本 |
 | `vehicle:online:{vehicleKey}` | 在线状态和 TTL |
 | `vehicle:protocols:{vehicleKey}` | 当前车辆最近出现过的协议集合 |

docs/go-version-data-flow.html

@@ -587,7 +587,7 @@
             <td><strong>Redis</strong></td>
             <td><code>vehicle:latest:{vehicle_key}:{protocol}</code></td>
             <td>realtime-api Kafka consumer</td>
-            <td>单协议实时快照</td>
+            <td>单协议实时轻量快照</td>
             <td>区分 32960/808/MQTT 的实时状态</td>
           </tr>
           <tr>

go/vehicle-gateway/internal/realtime/model.go

@@ -21,6 +21,11 @@ type Snapshot struct {
 	UpdatedAtMS    int64               `json:"updated_at_ms"`
 }
 
+func (s Snapshot) Lightweight() Snapshot {
+	s.Parsed = nil
+	return s
+}
+
 type OnlineStatus struct {
 	VehicleKey string              `json:"vehicle_key"`
 	VIN        string              `json:"vin"`

go/vehicle-gateway/internal/realtime/repository.go

@@ -55,13 +55,16 @@ func (r *Repository) Update(ctx context.Context, env envelope.FrameEnvelope) err
 	if err != nil && !errors.Is(err, redis.Nil) {
 		return err
 	}
+	existingParsed, err := r.GetRealtimeRaw(ctx, vehicleKey, env.Protocol)
+	if err != nil && !errors.Is(err, redis.Nil) {
+		return err
+	}
 	if existingProtocol.VehicleKey != "" {
 		protocolSnapshot = existingProtocol
 		if protocolSnapshot.VIN == "" && vin != "" {
 			protocolSnapshot.VIN = vin
 		}
 		mergeFields(&protocolSnapshot, env.Fields, eventMS)
-		protocolSnapshot.Parsed = mergeParsedForProtocol(env.Protocol, protocolSnapshot.Parsed, env.Parsed)
 		if eventMS >= protocolSnapshot.EventTimeMS {
 			protocolSnapshot.EventTimeMS = eventMS
 			protocolSnapshot.EventID = env.StableEventID()
@@ -70,7 +73,8 @@ func (r *Repository) Update(ctx context.Context, env envelope.FrameEnvelope) err
 		}
 		protocolSnapshot.UpdatedAtMS = nowMS
 	}
-	if err := r.setJSON(ctx, protocolKey(vehicleKey, env.Protocol), protocolSnapshot, r.cfg.ttl()); err != nil {
+	protocolSnapshot.Parsed = mergeParsedForProtocol(env.Protocol, existingParsed, env.Parsed)
+	if err := r.setJSON(ctx, protocolKey(vehicleKey, env.Protocol), protocolSnapshot.Lightweight(), r.cfg.ttl()); err != nil {
 		return err
 	}
 	if err := r.setJSON(ctx, realtimeRawKey(vehicleKey, env.Protocol), protocolSnapshot.Parsed, r.cfg.ttl()); err != nil {

go/vehicle-gateway/internal/realtime/repository_test.go

@@ -67,7 +67,7 @@ func TestRepositoryUpdatesMergedAndProtocolSnapshots(t *testing.T) {
 	}
 }
 
-func TestRepositoryStoresFullParsedProtocolSnapshotAndMergesGB32960Units(t *testing.T) {
+func TestRepositoryStoresFullParsedOnlyInRealtimeRawAndMergesGB32960Units(t *testing.T) {
 	repo, closeFn := newTestRepository(t)
 	defer closeFn()
 	ctx := context.Background()
@@ -110,9 +110,12 @@ func TestRepositoryStoresFullParsedProtocolSnapshotAndMergesGB32960Units(t *test
 	if err != nil {
 		t.Fatalf("GetRealtimeRaw() error = %v", err)
 	}
-	units := protocol.Parsed["data_units"].([]any)
-	if len(units) != 2 {
-		t.Fatalf("expected merged gb32960 units, got %#v", protocol.Parsed)
+	protocolJSON, err := json.Marshal(protocol)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if strings.Contains(string(protocolJSON), `"parsed"`) {
+		t.Fatalf("protocol snapshot should not duplicate full parsed data: %s", string(protocolJSON))
 	}
 	if len(realtimeRaw["data_units"].([]any)) != 2 {
 		t.Fatalf("realtime-raw did not keep merged parsed fields: %#v", realtimeRaw)