refactor: remaining game messages as structs, switch removed

Every game message still written or read by hand is now a NetGameMsg with
Serialize and Deserialize, in per-domain files:
- MovementMessages: teleport, platforms (resync and its request), orient to
  angle, node rotation lock, gravity scale, jetpack mode, control scheme,
  respawn checkpoint, rails (set/start, ready, cancel, arrived), mount
  inventory ID, dismount complete, possession ack, ghost reference override
  and position, camera cycling (eCameraTargetCyclingMode moves here).
- ZoneMessages: player loaded (the old PLAYER_LOADED case), ready for
  updates, player ready, restore to post load stats, server done loading,
  invalid zone transfer list, zone summary display/dismissed, level
  processing complete, object world state, and the localized announcement
  WorldMigration wrote by hand.
- PlayerMessages: chat mode, GM level, LEGO score, currency, reputation,
  GM invis, pickup currency, zone and player statistics, chat commands, bug
  reports, verify ack.
- ObjectMessages: fire event client/server side, notify client
  (zone) object, notify object, script network vars, failed preconditions,
  terminate interaction, set name, request use, request server object info.
- QuickBuildMessages: notify state, enable, cancel.
- ActivityMessages gains match response/update/request, leaderboard request
  and data, shooting gallery score/rotation/fire, activity state change.
- MissionMessages gains MissionDialogueCancelled (a no-op, as before).
The wire structs left in GameMessages.h move to their domains (tooltip and
emote to Effects, loot and item use to Inventory, model build to Building,
behavior sound to Property, skill sets to Skill) and gain the missing
direction. The dismount logic moves to PossessorComponent::OnDismountComplete.

Every inbound message is registered in the GameMessageHandler map; the
switch is gone, and GameMessages.cpp only holds the GameMsg/NetGameMsg base
code. Call sites build the structs (NotifyClientObject, TerminateInteraction,
Teleport, PlatformResync, FireEventClientSide, NotifyObject and
NotifyClientZoneObject get convenience constructors like PlayFXEffect).
Dead senders are dropped: SendSetShootingGalleryParams (no callers, field
order was a guess), SendTeamPickupItem (the struct already existed),
SendRequestActivitySummaryLeaderboardData (the struct covers it).

Verified with RemainingMessagesTests: every old Send* function is frozen
verbatim in Legacy/RemainingMessagesLegacy.h and compared byte for byte
(same bits, destination and broadcast flag) over grids of inputs; every old
Handle* read sequence is frozen as a Read* oracle and compared with the
struct's Deserialize; round trips, truncation and a golden packet.
PlayerLoaded (0x00dc36f0), SetGMLevel (0x00dd6230), MissionDialogueCancelled
(0x00d9cc10) and LocalizedAnnouncementServerToSingleClient (0x00f23c50)
were checked against the client. Behaviour notes: an inbound message that
fails to deserialize is dropped, so ParseChatMessage over MAX_MESSAGE_LENGTH
is dropped instead of truncated, and PLAYER_LOADED / READY_FOR_UPDATES /
MISSION_DIALOGUE_CANCELLED now read their (unused) client fields.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

dNet/BitStreamUtils.h

@@ -75,6 +75,7 @@ struct LUBitStream {
 };
 
 
+#define BITSTREAMUTILS_HAS_WRITEHEADER
 namespace BitStreamUtils {
 	template<typename T>
 	void WriteHeader(RakNet::BitStream& bitStream, ServiceType connectionType, T internalPacketID) {
@@ -124,6 +125,20 @@ namespace BitStreamUtils {
 	 * Reads a string written by WriteLengthPrefixed. Fails (returns false) if the stream runs out of data or
 	 * if the length is negative or larger than maxLength characters.
 	 */
+	/**
+	 * Writes name-value (LDF) text the way the client reads it: a u32 character count, the characters, and a null
+	 * terminator (not counted) when the text isn't empty.
+	 */
+	inline void WriteNameValueText(RakNet::BitStream& bitStream, const std::u16string& text) {
+		WriteLengthPrefixed<uint32_t>(bitStream, text);
+		if (!text.empty()) bitStream.Write<uint16_t>(0);
+	}
+
+	/**
+	 * Reads text written by WriteNameValueText (the null terminator is consumed and not kept).
+	 */
+	inline bool ReadNameValueText(RakNet::BitStream& bitStream, std::u16string& text, const uint32_t maxLength = 0x500000 /* MAX_MESSAGE_LENGTH */);
+
 	template<typename LenT = uint32_t, typename StringT>
 	bool ReadLengthPrefixed(RakNet::BitStream& bitStream, StringT& value, const uint32_t maxLength = 0x500000 /* MAX_MESSAGE_LENGTH */) {
 		LenT length{};
@@ -136,6 +151,12 @@ namespace BitStreamUtils {
 		if (length == 0) return true;
 		return bitStream.ReadBits(reinterpret_cast<unsigned char*>(value.data()), BYTES_TO_BITS(value.size() * sizeof(typename StringT::value_type)), true);
 	}
+
+	inline bool ReadNameValueText(RakNet::BitStream& bitStream, std::u16string& text, const uint32_t maxLength) {
+		if (!ReadLengthPrefixed<uint32_t>(bitStream, text, maxLength)) return false;
+		uint16_t terminator{};
+		return text.empty() || bitStream.Read(terminator);
+	}
 }
 
 namespace RakNet {