Add scalable OpenSans font test GUI and /kamkeel testfont command

[KAMKEEL]

Motivation

• Provide an example GUI demonstrating crisp, scalable text rendering using the existing TTF in resources and a client-side command to open it.
• Verify alignment and renderer behavior by showing baseline markers and renderer/atlas/debug info at multiple sizes.

Description

• Added a client GUI GuiFontTest that renders a title and sample text at sizes 8, 12, 16, 24, 32, 48, 64 with per-line baseline markers and debug text (renderer path, atlas dims, GUI scale, scale factor).
• Implemented ScalableSdfFontRenderer which loads assets/customnpcs/OpenSans.ttf from the classpath (ResourceLocation("customnpcs","OpenSans.ttf")), generates an SDF atlas and attempts GL20 shader rendering; if shader compilation fails it falls back to baking raster atlases per size (no single-bitmap upscaling); texture params set to linear filtering and clamp-to-edge and mipmaps disabled; GL state is saved/restored around rendering.
• Added GuiFontTestPacket (client-open packet) and TestCommand to expose /kamkeel testfont; registered the packet enum GUI_FONT_TEST, registered the packet in PacketHandler, and registered the command in the KAMKEEL command registry.
• Modified/added files:
  • Added: src/main/java/kamkeel/npcs/client/gui/GuiFontTest.java
  • Added: src/main/java/kamkeel/npcs/client/renderer/font/ScalableSdfFontRenderer.java
  • Added: src/main/java/kamkeel/npcs/command/TestCommand.java
  • Added: src/main/java/kamkeel/npcs/network/packets/data/gui/GuiFontTestPacket.java
  • Modified: src/main/java/kamkeel/npcs/command/CommandKamkeel.java
  • Modified: src/main/java/kamkeel/npcs/network/PacketHandler.java
  • Modified: src/main/java/kamkeel/npcs/network/enums/EnumDataPacket.java

Testing

• Initialized submodules as required with git submodule sync --recursive && git submodule update --init --recursive, which completed successfully.
• Verified the TTF location with rg --files src/main/resources | rg '\.ttf$' and found src/main/resources/assets/customnpcs/OpenSans.ttf.
• Built the project with ./gradlew compileJava and observed a successful build: BUILD SUCCESSFUL in 2m 11s (18 actionable tasks: 18 executed).

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