Fix in order to run with Alex's Mobs Neoforge 1.21.1

[crabsatellite]

AlexModGuy/AlexsMobs#2315

[Copilot]

Pull request overview

This pull request addresses compatibility issues to enable Citadel to run with Alex's Mobs on NeoForge 1.21.1. The changes primarily focus on event bus registration corrections, network packet direction fixes, shader configuration updates, and defensive null handling improvements.

• Event bus subscription annotations corrected to use MOD bus where appropriate
• Network packet registrations updated to reflect actual bidirectional and client/server-bound usage patterns
• Custom vertex shader introduced to replace vanilla shader reference for rainbow aura rendering
• Null safety improvements for transient fields and entity creation failure handling

Reviewed changes

Copilot reviewed 7 out of 9 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
src/main/resources/assets/citadel/shaders/core/rendertype_rainbow_aura.vsh	New vertex shader file added to replace vanilla "position_color_tex" reference
src/main/resources/assets/citadel/shaders/core/rendertype_rainbow_aura.json	Updated to reference custom vertex shader and reformatted for consistency
src/main/java/com/github/alexthe666/citadel/client/gui/data/LinkData.java	ItemStack field marked transient with null-safe getter to handle deserialization
src/main/java/com/github/alexthe666/citadel/client/gui/GuiBasicBook.java	Added blur effect override and exception handling for entity creation failures
src/main/java/com/github/alexthe666/citadel/client/gui/EntityLinkButton.java	Refactored entity creation to use getOptional() for safer registry lookups
src/main/java/com/github/alexthe666/citadel/client/ClientEvents.java	Corrected EventBusSubscriber annotation to specify MOD bus
src/main/java/com/github/alexthe666/citadel/Citadel.java	Fixed event bus registrations, packet directions, and conditional proxy registration
build.gradle	Added duplicatesStrategy to prevent build errors from duplicate resources
.gitignore	Added .vscode directory to ignore list

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[AlexModGuy]

Merged. Awaiting other PR #218 to be updated before merging that and uploading to curseforge and modrinth.