chore: purge MCreator remnants (project is now fully hand-maintained)

- Remove 'MCreator note: REGENERATED' headers and user-code-block
  markers (no regeneration step exists anymore)
- Remove MCreator mentions from mod credits/authors
- AGENTS.md: replace the MCreator code-preservation rules with a code
  ownership section

AGENTS.md

@@ -1,6 +1,6 @@
 # Custom Ore Gem - Developer Guide for Agents
 
-This repository is a Minecraft **NeoForge 1.21.1** mod created with **MCreator**. Agents must follow these strict guidelines to ensure build stability and code preservation.
+This repository is a Minecraft **NeoForge 1.21.1** mod. It was originally scaffolded with MCreator but is now **fully hand-maintained** — all files are safe to edit. Agents must follow these guidelines to ensure build stability.
 
 ## 1. Build & Test Commands
 
@@ -49,27 +49,14 @@ Use the Gradle wrapper for all operations. Ensure you are using Java 21 (NeoForg
   ./gradlew clean
   ```
 
-## 2. MCreator & Code Preservation
+## 2. Code Ownership
 
-**CRITICAL:** This project is partially generated by MCreator.
-- **Generated Files:** Many files in `src/main/java` are regenerated on every build or MCreator export.
-- **User Code Blocks:** You **MUST** only edit code within designated user code blocks in these files.
-  ```java
-  // Start of user code block [block_name]
-  // ... YOUR CODE HERE ...
-  // End of user code block [block_name]
-  ```
-  - If a file does not have these blocks, assume it is **UNSAFE** to edit unless you created it yourself.
-
-- **Safe Files:**
-  - Files strictly created by you (e.g., in `src/test/java`).
-  - New utility classes or event handlers not managed by MCreator.
-  
-- **Do NOT** directly modify the following unless inside a user block:
-  - `CustomOreGenModBlocks.java`
-  - `CustomOreGenModItems.java`
-  - `CustomOreGenModTabs.java`
-  - Any file in `net.mcreator.customoregen.procedures` (unless explicitly safe).
+The project was originally generated by MCreator but is no longer maintained with it
+(MCreator is not installed anymore; the build is plain Gradle + NeoForge ModDev).
+- **Every file** in `src/main/java` and `src/test/java` is hand-maintained and safe to edit.
+- The historical "user code block" markers were removed; there is no regeneration step.
+- Keep MCreator-era naming quirks (e.g. `SharddiamondpickaxeItem`) unless a rename is
+  explicitly requested, to keep diffs readable.
 
 ## 3. Code Style & Conventions