Mod textures, display names, and atlas injection

Mod Atlas (ModAtlas.cpp/h):
- Build merged terrain.png and items.png from mod assets (blocks/*.png, items/*.png)
- Scan vanilla atlas for empty (fully transparent) cells; place mod textures only there
- Install merged atlases over game files before Minecraft::init; restore originals after
- Hook loadUVs to create SimpleIcon objects for mod textures
- Hook registerIcon to return mod icons when requested by name
- FixupModIcons: copy field_0x48 (source-image ptr) from vanilla icons after init

Mod Strings (ModStrings.cpp/h):
- Store mod display names by description ID
- Hook GetString to serve mod names for blocks/items

API changes:
- BlockProperties/ItemProperties: .Name(displayName), namespaced .Icon()
- NativeInterop: displayName params, native_allocate_description_id, native_register_string
- Registry.Assets for string registration
- Output: mods/LegacyForge.API/, mods/ExampleMod/ (per-mod folders)

Mod discovery:
- Scan mods/*/ for mod folders; load DLLs from each
- LegacyForge.API as mod in mods/LegacyForge.API/

ExampleMod:
- Ruby ore block and ruby item with custom textures and names
- Assets: blocks/ruby_ore.png, items/ruby.png, lang files
- Furnace recipe: ruby_ore -> ruby

Runtime: loadUVs, registerIcon, getResourceAsStream, GetString hooks; stb_image for PNG

ExampleMod/assets/README.md

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+# ExampleMod Assets
+
+## Language files
+
+Language files live in `assets/lang/` with the format `{locale}.lang` (e.g. `en-GB.lang`, `de-DE.lang`).
+
+**Current API:** Use `BlockProperties.Name()` and `ItemProperties.Name()` when registering blocks and items. These set the display name shown in-game. The ModLoader hooks into the game's string lookup so your names appear correctly.
+
+**Future:** Multi-locale support may load from these `.lang` files. Format: `key=value` per line, with `#` for comments.
+
+## Textures
+
+Mod textures are supported via the dynamic atlas system. Place PNG files in:
+
+- **Blocks:** `assets/blocks/{name}.png` → icon `{modid}:{name}` (e.g. `ruby_ore.png` → `examplemod:ruby_ore`)
+- **Items:** `assets/items/{name}.png` → icon `{modid}:{name}` (e.g. `ruby.png` → `examplemod:ruby`)
+
+The mod ID is derived from the mod folder name (lowercase, hyphens removed). Use the namespaced icon in `BlockProperties.Icon()` and `ItemProperties.Icon()`:
+
+```csharp
+.Icon("examplemod:ruby_ore")  // block from assets/blocks/ruby_ore.png
+.Icon("examplemod:ruby")      // item from assets/items/ruby.png
+```
+
+Textures must be 16×16 pixels (or any size; they are scaled). For vanilla icons, use names like `gold_ore`, `diamond`, etc.

ExampleMod/assets/lang/de-DE.lang

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+# ExampleMod language file (de-DE)
+# German translations for ExampleMod content.
+
+block.examplemod.ruby_ore=Rubinerz
+item.examplemod.ruby=Rubin

ExampleMod/assets/lang/en-GB.lang

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+# ExampleMod language file (en-GB)
+# Display names for blocks and items.
+# In the current API, use BlockProperties.Name() and ItemProperties.Name() instead.
+# This file documents the expected format for future multi-locale support.
+
+block.examplemod.ruby_ore=Ruby Ore
+item.examplemod.ruby=Ruby