Add back BuildableComponent

[jpenilla]

Summary

Restore binary compatibility for 4.x-compiled component builder calls that expect build(): BuildableComponent.

Adventure 5 changed ComponentBuilder#build’s erased return type from the old BuildableComponent hierarchy to Component. Code compiled against Adventure 4.x can therefore fail at runtime on Adventure 5.x with:

NoSuchMethodError: TextComponent$Builder.build():BuildableComponent

Fixes #1431.

Changes

• Reintroduce BuildableComponent as a deprecated, for-removal compatibility type.
• Make component interfaces assignable to BuildableComponent again.
• Extend the existing legacy ABI patch plugin to inject a synthetic bridge:

ComponentBuilder.build():BuildableComponent

in addition to the existing build():Object bridge.

The public source API remains based on ComponentBuilder<C extends Component, ...>, so normal newly compiled 5.x code continues to target the modern ABI:

build():Component

To emit bytecode referencing the restored legacy bridge, code must explicitly use the deprecated compatibility type, for example:

BuildableComponent<?, ?> component = Component.text().build();

That usage produces deprecation/removal warnings and is not intended for new code.

Compatibility notes

This supports:

• 4.x-compiled code running on Adventure 5.x

It does not make 5.x-compiled code run on Adventure 4.x, and it does not make BuildableComponent a supported long-term API again. The restored type and bridge should be removed in 6.x.

Verification

• Verified that 4.26.1-compiled bytecode calling:

TextComponent$Builder.build():BuildableComponent

runs successfully against the rebuilt 5.x jar.

• Verified that normal newly compiled 5.x code still emits:

TextComponent$Builder.build():Component

for Component.text().build().

• Verified that bytecode only references BuildableComponent when source explicitly uses the deprecated BuildableComponent type.