Metin2 game client (P0–P11) + mobile asset pipeline

Networked client on the existing Godot 4.7 + libgr2 renderer:
- net: m2dev wire protocol (libsodium KX + XChaCha20), auth/select/game
  phases, EntityStore world model, ~all GC/CG headers. char create/delete,
  private shop / mall / cube, SHOP_GC_START_EX, guild, party (+ CG_PARTY_SET_STATE),
  quests, dragon soul, refine, safebox, exchange.
- UI: in-game windows migrated 1:1 from the reference uiscript/root .py —
  char status (/stat), inventory+equipment, select-item ([SELECT_ITEM] quest
  token), system-option + game-option + ESC system menu, private-shop 39-grid,
  party info board, shop tabs, atlas, minimap, quickbar, chat, …
- EterGrnLib polish: GR2 material blend/two-sided, LOD crossfade, motion-event
  dispatch, contact shadow, ray-AABB picking, weapon grip pre-transform.

Portable asset IO (A1) — all extension/libgr2/formats/mtproto reads routed
through godot::FileAccess (res:// PCK works on iOS/Android); standalone-lib
*_path() kept for the non-Godot CTests. AssetResolver + PropertyRegistry
switched to a baked index (bake_asset_index.gd) instead of std::filesystem.

Mobile builds: build-{android,ios}.sh, export-android.sh, pack-assets.sh,
gen-debug-keystore.sh. Assets ship as a zip mounted at runtime by
project/asset_pack.gd (adb push now; HTTP download is a drop-in later).

ctest 10/10, 34 GDScript suites, macOS/iOS/Android all build.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013EJxkHiNKS4kybHS3XKyAJ

extension/src/water_builder.h

@@ -0,0 +1,30 @@
+#pragma once
+
+#include <godot_cpp/classes/array_mesh.hpp>
+#include <godot_cpp/classes/ref.hpp>
+
+#include <terrain_files.h>
+
+#include <vector>
+
+namespace fmt {
+struct AssetResolver;
+}
+
+// W7 / PARITY §4 —— water.wtr -> 每层水面网格（texel 掩膜）+ 共享水材质。
+// 水材质用原客户端资产：`special/water/01..30.dds` 30 帧序列（`MapOutdoorWater.cpp:14/43`，
+// 70ms/帧），UV 平铺频率 = 1/(CELLSCALE*4)（每 4 格一循环），逐顶点水深 alpha，轻微高度浮动。
+namespace mtgodot {
+
+struct WaterPiece {
+	godot::Ref<godot::ArrayMesh> mesh; // Godot 空间，已含区块原点
+	float godot_y = 0;
+};
+
+// hm/height_scale 用来算每个水面顶点下方的地形高度 -> 水深 -> alpha。
+std::vector<WaterPiece> build_chunk_water(const fmt::WaterMap &wm, const fmt::HeightMap &hm,
+		int tile_x, int tile_y, double height_scale, const fmt::AssetResolver &res);
+
+void cleanup_water_shader();
+
+} // namespace mtgodot