Rebrand LegacyForge to Weave Loader

Rename across entire codebase:
- LegacyForge -> WeaveLoader (identifiers, namespaces, classes, DLLs)
- LegacyForgeRuntime -> WeaveLoaderRuntime (C++ project)
- LegacyForge.API/Core/Launcher -> WeaveLoader.API/Core/Launcher (C# projects)
- [LegacyForge] -> [WeaveLoader] (log prefixes)
- legacyforge -> weaveloader (config files, log files, backup suffixes)
- Display name "Weave Loader" in README, CONTRIBUTING, LICENSE

WeaveLoader.API/Block/BlockRegistry.cs

@@ -0,0 +1,58 @@
+namespace WeaveLoader.API.Block;
+
+/// <summary>
+/// Represents a block that has been registered with the game engine.
+/// </summary>
+public class RegisteredBlock
+{
+    /// <summary>The namespaced string ID (e.g. "mymod:ruby_ore").</summary>
+    public Identifier StringId { get; }
+
+    /// <summary>The numeric ID allocated by the engine.</summary>
+    public int NumericId { get; }
+
+    internal RegisteredBlock(Identifier id, int numericId)
+    {
+        StringId = id;
+        NumericId = numericId;
+    }
+}
+
+/// <summary>
+/// Block registration via the WeaveLoader registry.
+/// Accessed through <see cref="Registry.Block"/>.
+/// </summary>
+public static class BlockRegistry
+{
+    /// <summary>
+    /// Register a new block with the game engine.
+    /// </summary>
+    /// <param name="id">Namespaced identifier (e.g. "mymod:ruby_ore").</param>
+    /// <param name="properties">Block properties built with <see cref="BlockProperties"/>.</param>
+    /// <returns>A handle to the registered block.</returns>
+    public static RegisteredBlock Register(Identifier id, BlockProperties properties)
+    {
+        int numericId = NativeInterop.native_register_block(
+            id.ToString(),
+            (int)properties.MaterialValue,
+            properties.HardnessValue,
+            properties.ResistanceValue,
+            (int)properties.SoundValue,
+            properties.IconValue,
+            properties.LightEmissionValue,
+            properties.LightBlockValue,
+            properties.NameValue ?? "");
+
+        if (numericId < 0)
+            throw new InvalidOperationException($"Failed to register block '{id}'. No free IDs or invalid parameters.");
+
+        if (properties.CreativeTabValue != CreativeTab.None)
+        {
+            NativeInterop.native_add_to_creative(numericId, 1, 0, (int)properties.CreativeTabValue);
+            Logger.Debug($"Block '{id}' added to creative tab {properties.CreativeTabValue}");
+        }
+
+        Logger.Debug($"Registered block '{id}' -> numeric ID {numericId}");
+        return new RegisteredBlock(id, numericId);
+    }
+}