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

formats/terrain_mesh.cpp

@@ -0,0 +1,102 @@
+#include "terrain_mesh.h"
+
+#include "m2_coord.h"
+
+#include <algorithm>
+#include <cmath>
+
+namespace fmt {
+
+namespace {
+constexpr int CS = m2coord::CELLSCALE;          // 200 cm
+constexpr double CS_M = double(CS) * m2coord::CM_TO_M; // 2.0 m
+} // namespace
+
+double terrain_height_at(const HeightMap& hm, double lx_cm, double ly_cm, double hs) {
+    // 照 CTerrain::GetHeight（本地坐标版，调用方已把全局->本地 + y 取绝对值）
+    if (lx_cm < 0 || ly_cm < 0 || lx_cm > double(m2coord::TERRAIN_SIZE) * CS ||
+        ly_cm > double(m2coord::TERRAIN_SIZE) * CS)
+        return 0.0;
+
+    long xi = (long)lx_cm, yi = (long)ly_cm;
+    long xdist = xi % CS, ydist = yi % CS;
+    long x = xi / CS, y = yi / CS;
+    const double oo = 1.0 / double(CS);
+
+    double h1 = hm.at((int)x, (int)y) * hs;         // TL
+    double h2 = hm.at((int)x + 1, (int)y + 1) * hs; // BR
+    if (xdist <= ydist) {                            // 左三角：TL, BR, BL
+        double h3 = hm.at((int)x, (int)y + 1) * hs;
+        double xslope = (h2 - h3) * oo;
+        double yslope = (h3 - h1) * oo;
+        return h1 + (xdist * xslope + ydist * yslope);
+    }
+    // 右三角：TL, BR, TR
+    double h3 = hm.at((int)x + 1, (int)y) * hs;
+    double xslope = (h3 - h1) * oo;
+    double yslope = (h2 - h3) * oo;
+    return h1 + (xdist * xslope + ydist * yslope);
+}
+
+void build_terrain_mesh(const HeightMap& hm, int tile_x, int tile_y, double hs,
+                        TerrainMesh& out, bool ccw_from_above) {
+    out = TerrainMesh{};
+    const int N = TerrainMesh::VERTS_XY; // 129
+    out.positions.resize(size_t(N) * N * 3);
+    out.normals.resize(size_t(N) * N * 3);
+    out.uvs.resize(size_t(N) * N * 2);
+    out.indices.reserve(size_t(TerrainMesh::QUADS_XY) * TerrainMesh::QUADS_XY * 6);
+
+    // Godot 空间原点：见 area_data.h 说明 —— 区块 y 取负，position_to_godot 再翻正。
+    const double X0 = double(tile_x) * m2coord::CHUNK_CM * m2coord::CM_TO_M;
+    const double Z0 = double(tile_y) * m2coord::CHUNK_CM * m2coord::CM_TO_M;
+
+    auto height_m = [&](int i, int j) -> double {
+        return hm.at(i, j) * hs * m2coord::CM_TO_M;
+    };
+
+    double miny = 1e30, maxy = -1e30;
+    for (int j = 0; j < N; ++j) {
+        for (int i = 0; i < N; ++i) {
+            const double gy = height_m(i, j);
+            const size_t o = (size_t(j) * N + i) * 3;
+            out.positions[o + 0] = float(X0 + i * CS_M);
+            out.positions[o + 1] = float(gy);
+            out.positions[o + 2] = float(Z0 + j * CS_M);
+            const size_t uo = (size_t(j) * N + i) * 2;
+            out.uvs[uo + 0] = float(i) / float(TerrainMesh::QUADS_XY);
+            out.uvs[uo + 1] = float(j) / float(TerrainMesh::QUADS_XY);
+            miny = std::min(miny, gy);
+            maxy = std::max(maxy, gy);
+
+            // 中心差分（用边界样本，跨区块无缝）；y=f(x,z) 的法线 = (-df/dx, 1, -df/dz)
+            const double dh_di = (height_m(i + 1, j) - height_m(i - 1, j)) / (2.0 * CS_M);
+            const double dh_dj = (height_m(i, j + 1) - height_m(i, j - 1)) / (2.0 * CS_M);
+            double nx = -dh_di, ny = 1.0, nz = -dh_dj;
+            const double len = std::sqrt(nx * nx + ny * ny + nz * nz);
+            out.normals[o + 0] = float(nx / len);
+            out.normals[o + 1] = float(ny / len);
+            out.normals[o + 2] = float(nz / len);
+        }
+    }
+    out.min_y = float(miny);
+    out.max_y = float(maxy);
+
+    auto vid = [N](int i, int j) { return int32_t(j * N + i); };
+    for (int j = 0; j < TerrainMesh::QUADS_XY; ++j) {
+        for (int i = 0; i < TerrainMesh::QUADS_XY; ++i) {
+            int32_t TL = vid(i, j), TR = vid(i + 1, j);
+            int32_t BL = vid(i, j + 1), BR = vid(i + 1, j + 1);
+            // 对角线 TL-BR（= GetHeight 的 h1/h2）
+            if (ccw_from_above) {
+                out.indices.insert(out.indices.end(), {TL, BR, BL});
+                out.indices.insert(out.indices.end(), {TL, TR, BR});
+            } else {
+                out.indices.insert(out.indices.end(), {TL, BL, BR});
+                out.indices.insert(out.indices.end(), {TL, BR, TR});
+            }
+        }
+    }
+}
+
+} // namespace fmt