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

test/shear-bones-survey.md

@@ -0,0 +1,37 @@
+# Shear-bone survey (Godot GPU-skinning viability)
+
+`tools/anim_probe <model.gr2> <anim.gr2>` — for every bone, the parent-relative
+local that would be fed to `Skeleton3D::set_bone_pose`, its shear, and the error
+of a `T·R(quat)·S` round-trip (= what Godot's GPU vertex skinning keeps after it
+orthonormalizes the bone matrix before upload). High round-trip error = that bone
+**collapses on the GPU (Skeleton3D) path once an animation moves it**.
+
+Probed with `pc/warrior/action/dance_1.gr2` (retarget by bone name; unmatched
+bones sit at bind, so their numbers reflect the model's rest rig).
+
+| model | shear bones | worst TRS err | worst minDet | GPU-skin viable? |
+|---|---|---|---|---|
+| `warrior_cheongrin` | **7** (`bone_front_01..04`, `Bone_shoulder_01..04`) | 0.94 | 0.065 (6.5% squash) | ❌ collapses (`dance_1` animates these) |
+| `assassin` | 0 | — | — | ✅ |
+| `sura_lord` | **16** (`Bone05/06`, `Bone14..27`) | **1.52** | **0.0024** (0.24% squash) | ❌❌ severe |
+| `shaman_lord` | 0 | — | — | ✅ |
+
+## Takeaways
+
+- The shear/non-uniform-scale is **baked into the rest rig** of these cloth/plate
+  helper bones (metrics are constant across the animation clock). Static bind pose
+  survives because `skin_matrix ≈ I` there; any animation that moves a shear bone
+  breaks it on GPU skinning.
+- **`sura` is unusable on Godot's built-in GPU skinning** — 16 bones, one squashed
+  to 0.24%. It's a core class, so this isn't a corner case.
+- `assassin` / `shaman` are clean — GPU skinning would be fine for them.
+- **Done (2026-08-29)**: the custom skinning vertex shader is implemented —
+  `m2_material.cpp` `SRC_SKIN` does LBS with the full per-bone 4×3 matrices from an
+  RGBAF texture (`Metin2Model::gpu_skin` fills it each frame), no `Skeleton3D`, no
+  orthonormalization. `MTGODOT_GPUSKIN=1` now routes here (the old broken
+  `set_bone_pose` path is deleted). warrior `dance_1` GPU render == CPU render
+  (`test/compare-shots/*.gpu.png`). CPU LBS stays the default; GPU is for crowds
+  (Phase 2 bench).
+
+Re-run for a full race sweep (incl. monsters, NPCs, mounts) before Phase 2 to
+size the shader work and catch any rig that also needs >4 bone influences.