feat: port GaC-hkrpg-ps to Go with SceneCastSkill camera-detach fix

- mihoyo-variant KCP in pure Go (28-byte conv+token header), UDP gateway
  with 0xFF/0x145/0x194 handshake, ms-precision KCP clock + retransmit ticker
- protobuf for 4.6.51 generated from the AstralOS StarRail.proto (4932
  messages) plus CmdID map from // CmdID: comments (2114 ids)
- sdkserver port: query_dispatch/query_gateway (Gateserver pb + base64),
  hotfix fetch, auth endpoints, SRTools freesr-data.json upload
- gameserver handlers: login flow, scene load/spawn with real monster
  entity tracking, lineup, avatar/skin, missions, tutorials (1249+855),
  bag/equip, challenge incl. StartChallenge 1787 layout + Tierce 8973 +
  peak 8948, all raw tierce replies
- SceneCastSkill camera bug fix: only real scene monsters (tracked per
  session) trigger battle; attacking props/NPCs/air replies retcode 0
  without battle_info so the camera stays locked on the character
- end-to-end smoke test simulating a client over real UDP: handshake,
  PlayerGetToken, and both SceneCastSkill paths
- reuses the Rust PS data files unchanged (freesr-data.json, persistent,
  res.json, teleports.json, challenge_data.json, mission_unlocks.json)

internal/common/res.go

@@ -0,0 +1,134 @@
+package common
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"sync"
+	"time"
+)
+
+// LogInfo prints a timestamped info line (kept dependency-free).
+func LogInfo(format string, args ...any) {
+	fmt.Printf("%s %s\n", time.Now().Format("2006-01-02 15:04:05"), fmt.Sprintf(format, args...))
+}
+
+// ---------------------------------------------------------------------------
+// res.json (camelCase, produced by the AstralOS dump pipeline)
+// ---------------------------------------------------------------------------
+
+type Vector struct {
+	X int32 `json:"x"`
+	Y int32 `json:"y"`
+	Z int32 `json:"z"`
+}
+
+type SceneMonsterInfo struct {
+	Pos       Vector `json:"pos"`
+	Rot       Vector `json:"rot"`
+	GroupID   uint32 `json:"groupId"`
+	InstID    uint32 `json:"instId"`
+	MonsterID uint32 `json:"monsterId"`
+	EventID   uint32 `json:"eventId"`
+}
+
+type SceneNpcInfo struct {
+	Pos     Vector `json:"pos"`
+	Rot     Vector `json:"rot"`
+	GroupID uint32 `json:"groupId"`
+	InstID  uint32 `json:"instId"`
+	NpcID   uint32 `json:"npcId"`
+}
+
+type ScenePropInfo struct {
+	Pos       Vector `json:"pos"`
+	Rot       Vector `json:"rot"`
+	GroupID   uint32 `json:"groupId"`
+	InstID    uint32 `json:"instId"`
+	PropState uint32 `json:"propState"`
+	PropID    uint32 `json:"propId"`
+}
+
+type TeleportInfo struct {
+	Pos Vector `json:"pos"`
+	Rot Vector `json:"rot"`
+}
+
+type SceneData struct {
+	Npcs                 []SceneNpcInfo          `json:"npcs"`
+	Props                []ScenePropInfo         `json:"props"`
+	Monsters             []SceneMonsterInfo      `json:"monsters"`
+	Teleports            map[uint32]TeleportInfo `json:"teleports"`
+	FinishedSubMissions  []uint32                `json:"finishedSubMissions"`
+	FinishedMainMissions []uint32                `json:"finishedMainMissions"`
+	Chests               []uint32                `json:"chests"`
+}
+
+type LevelOutputConfig struct {
+	IsEnteredSceneInfo bool                 `json:"isEnteredSceneInfo"`
+	Scenes             map[uint32]SceneData `json:"scenes"`
+	PlaneType          uint32               `json:"planeType"`
+	WorldID            uint32               `json:"worldId"`
+	Sections           []uint32             `json:"sections"`
+	SavedValues        map[string]int32     `json:"savedValues"`
+}
+
+type AvatarConfig struct {
+	WeaknessBuffID uint32 `json:"weaknessBuffId"`
+}
+
+type JsonConfig struct {
+	// entryId -> "P<plane>_F<floor>" -> config
+	LevelOutputConfigs    map[uint32]map[string]*LevelOutputConfig `json:"levelOutputConfigs"`
+	AvatarConfigs         map[uint32]AvatarConfig                  `json:"avatarConfigs"`
+	MapDefaultEntranceMap map[uint32]uint32                        `json:"mapDefaultEntranceMap"`
+	RelicAvatarRecommend  map[uint32][]uint32                      `json:"relicAvatarRecommend"`
+	SkinIDs               []uint32                                 `json:"skinIds"`
+}
+
+var (
+	gameResOnce  sync.Once
+	gameRes      *JsonConfig
+	gameResErr   error
+	teleportOnce sync.Once
+	teleportDB   map[uint32]map[uint32]TeleportInfo
+)
+
+// GameRes lazily parses res.json (13MB; parsed once).
+func GameRes() (*JsonConfig, error) {
+	gameResOnce.Do(func() {
+		gameRes = &JsonConfig{}
+		raw, err := os.ReadFile("res.json")
+		if err != nil {
+			gameResErr = err
+			return
+		}
+		if err := json.Unmarshal(raw, gameRes); err != nil {
+			gameResErr = fmt.Errorf("res.json is malformed: %w", err)
+			return
+		}
+		if gameRes.LevelOutputConfigs == nil {
+			gameRes.LevelOutputConfigs = map[uint32]map[string]*LevelOutputConfig{}
+		}
+		if gameRes.AvatarConfigs == nil {
+			gameRes.AvatarConfigs = map[uint32]AvatarConfig{}
+		}
+		if gameRes.MapDefaultEntranceMap == nil {
+			gameRes.MapDefaultEntranceMap = map[uint32]uint32{}
+		}
+	})
+	return gameRes, gameResErr
+}
+
+// Teleports lazily parses teleports.json ({floor_id: {teleport_id: info}}).
+func Teleports() map[uint32]map[uint32]TeleportInfo {
+	teleportOnce.Do(func() {
+		teleportDB = map[uint32]map[uint32]TeleportInfo{}
+		raw, err := os.ReadFile("teleports.json")
+		if err != nil {
+			return
+		}
+		_ = json.Unmarshal(raw, &teleportDB)
+	})
+	return teleportDB
+}