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/gameserver/handlers_authentication.go

@@ -0,0 +1,36 @@
+package gameserver
+
+import (
+	"time"
+
+	goproto "gac-hkrpg-go/protocol/proto"
+)
+
+const playerUID uint32 = 1337
+
+func init() {
+	handle("PlayerGetToken", func(s *Session, req *goproto.PlayerGetTokenCsReq, rsp *goproto.PlayerGetTokenScRsp) error {
+		rsp.Retcode = 0
+		rsp.Msg = "OK"
+		rsp.Uid = playerUID
+		return nil
+	})
+
+	handle("PlayerLogin", func(s *Session, req *goproto.PlayerLoginCsReq, rsp *goproto.PlayerLoginScRsp) error {
+		rsp.Retcode = 0
+		rsp.CurTimezone = 8
+		rsp.LoginRandom = req.LoginRandom
+		rsp.ServerTimestampMs = uint64(time.Now().UnixMilli())
+		rsp.Stamina = 240
+		rsp.BasicInfo = &goproto.PlayerBasicInfo{
+			Nickname:   "RobinSR",
+			Level:      70,
+			WorldLevel: 6,
+			Stamina:    240,
+			Mcoin:      9999999,
+			Hcoin:      9999999,
+			Scoin:      9999999,
+		}
+		return nil
+	})
+}