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/tree_placeholder.h

@@ -0,0 +1,34 @@
+#pragma once
+
+#include <godot_cpp/classes/array_mesh.hpp>
+#include <godot_cpp/classes/ref.hpp>
+#include <godot_cpp/variant/string.hpp>
+
+#include <string>
+
+namespace fmt {
+struct AssetResolver;
+}
+
+// W4/R2 —— `.spt` 几何尚未跨平台读取（见 formats/spt.h），运行时使用 tree proxy：
+// 确定性枝干 + 多组交叉叶簇，并优先采用 .spt 指向的真实 bark/composite DDS。
+// 一份共享 mesh / treefile，逐实例只由 MultiMesh 承载原 AreaData 位置。
+namespace mtgodot {
+
+// species_hint = treefile 名（判针叶/阔叶）。height_m ≈ 期望树高（米）。
+godot::Ref<godot::ArrayMesh> build_placeholder_tree(const godot::String &species_hint,
+		float height_m = 12.0f);
+
+// R2 tree proxy：保留无专有运行时的限制，但从 .spt 嗅探真实树皮和 composite atlas，
+// 用确定性的枝干/叶簇 mesh 近似 SpeedTree 的 branch/frond/leaf 分层。结果按 treefile 缓存，
+// 可安全用于每树种一个 MultiMesh。若资源解析失败，自动退回纯程序化材质。
+godot::Ref<godot::ArrayMesh> get_tree_proxy_mesh(const std::string &treefile,
+		const fmt::AssetResolver &resolver, float height_m = 12.0f);
+
+// 从 treefile 名猜是否针叶（cedar / cypress / pine / fir / spruce…）。
+bool species_is_conifer(const godot::String &species_hint);
+
+// 退出时清 shader、DDS 和 treefile->mesh 缓存。
+void cleanup_tree_shader();
+
+} // namespace mtgodot