Fix AttributeModifier serialization, download exception handling, selector nullability, and relocation package naming

[Spagles]

Description

• AttributeModifier Serialization: Added ATTRIBUTE_MODIFIER_GET_AMOUNT_METHOD to RefAttributeModifier and updated AttributeModifierSerializer#serialize to write the required "amount" field during serialization.
• Dependency Downloader Fail-Safe: Updated AnnoyingDownload#downloadFile to catch IOException during stream operations, properly invoking fail(dependency, platform) to attempt fallback platforms instead of logging false success and loading corrupt/empty files.
• Selector Optional Null Safety: Added raw == null checks to SelectorOptional#orElse, orElseSingle, and orElseFlat to prevent passing null to @NotNull Function arguments when no input is supplied.
• Relocation Package Parsing: Updated AnnoyingPlugin#getRelocation to safely compute package name indices when standard dot-separated package strings (without {} delimiters) are provided.

Motivation and Context

• Deserializing AttributeModifier objects failed with IllegalArgumentException("Missing required field: amount") due to missing serialization output.
• Failed network requests or interrupted downloads in AnnoyingDownload were swallowed silently, causing invalid JARs to be passed to Bukkit's plugin manager.
• Command selector resolution threw NullPointerException when evaluating default functions for absent command arguments.
• Standard package strings passed to getRelocation resulted in corrupted package target paths (e.g. "org.reflections" becoming "rg.reflections").

How Has This Been Tested?

• Executed unit test suite (./gradlew test) including AttributeModifierSerializerTest, ConfigMigrationTest, and storage dialect tests using MockBukkit.
• Verified round-trip serialization of AttributeModifier and valid handling of dependency download fallbacks.

Media:

N/A

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have read the CONTRIBUTING document.
• All new and existing tests passed.

[srnyx]

thanks

[StormCode-dev]

Hey. Just wanted to give you a heads up that the account activity for Spagles is incredibly odd, and of the four commits they added to my forked repo, proved to be flat-out wrong or generally avoided practice. I'd probably double check the account's changes again, just in case.

[srnyx]

Hey. Just wanted to give you a heads up that the account activity for Spagles is incredibly odd, and of the four commits they added to my forked repo, proved to be flat-out wrong or generally avoided practice. I'd probably double check the account's changes again, just in case.

hi, thanks. yeah i can tell this entire PR was AI-generated (would be nice if they said that) so i triple-checked everything and discussed with some other ppl. the changes here are super minimal and all okay. appreciate the heads up.