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/gr2_bridge.h

@@ -14,6 +14,9 @@
 
 #include <gr2/gr2.h>
 
+#include <cstdint>
+#include <vector>
+
 namespace godot {
 class Skeleton3D;
 class Skin;
@@ -25,6 +28,10 @@ namespace mtgodot {
 // 4x4 transpose: gr2 row-major/row-vector -> Godot Transform3D.
 godot::Transform3D gr2_to_godot(const gr2::Mat4 &m);
 
+// gr2 affine compose (row-vector: result applies A then B), same as libgr2's
+// internal mul4x3. R = A · B with the 4th row treated as translation.
+gr2::Mat4 mul4x3(const gr2::Mat4 &A, const gr2::Mat4 &B);
+
 // Z-up cm -> Y-up m (+ optional Z flip for LH->RH content).
 godot::Transform3D make_conv(float unit_scale, bool flip_z);
 
@@ -32,15 +39,27 @@ godot::Transform3D make_conv(float unit_scale, bool flip_z);
 // folded into root bones). Returns nullptr if the skeleton has no bones.
 godot::Skeleton3D *build_skeleton(const gr2::Skeleton &sk);
 
+// One render part = one Godot surface. A gr2 mesh with N>1 tri_groups splits into
+// N parts (each its own material); a mesh with 0/1 groups is one whole-mesh part.
+struct RenderPart {
+	int mesh = -1;          // gr2::FileInfo::meshes index
+	int group = -1;         // gr2::Mesh::tri_groups index, or -1 = whole mesh
+	int mat_index = -1;     // tri_groups[group].material_index (mesh-local), or -1
+	uint32_t idx_first = 0; // start into mesh.indices  (= tri_first * 3)
+	uint32_t idx_count = 0; // length into mesh.indices (= tri_count * 3)
+};
+std::vector<RenderPart> build_parts(const gr2::FileInfo &fi);
+
 // Skin whose bind list is parallel to the skeleton bones:
 //   bind i  ->  bone i,  pose = gr2_to_godot(bone[i].inverse_world)
 godot::Ref<godot::Skin> build_skin(const gr2::Skeleton &sk);
 
-// One ArrayMesh with a surface per gr2 Mesh that has geometry.
+// One ArrayMesh with a surface per RenderPart (see build_parts).
 // ARRAY_BONES values are skeleton bone indices (mesh slot -> bone via
 // mesh.bone_bindings). Rigid meshes are bound rigidly to bone_bindings[0].
 // Fills out_bounds with the untransformed vertex AABB.
-godot::Ref<godot::ArrayMesh> build_mesh(const gr2::FileInfo &fi, bool flip_winding,
+godot::Ref<godot::ArrayMesh> build_mesh(const gr2::FileInfo &fi,
+		const std::vector<RenderPart> &parts, bool flip_winding,
 		godot::AABB &out_bounds);
 
 } // namespace mtgodot