[pjscruggs]

Adds a separate fabric-26 artifact for Minecraft 26.1 through 26.3 using deobfuscated production names. The existing fabric artifact retains intermediary names for Minecraft 1.18 through 1.21.x. Both share source, with separate Minecraft, Java and loader requirements.

Packet aliases are generated from versioned mappings at build time, so normal 26.x launches do not need runtime mappings. The port updates encryption and protocol-transition hooks, skips a removed legacy mixin, and classifies the new play packets. Proxy mappings add protocols 775, 776 and 777 while retaining the older records.

Builds and CI use Java 25. The retired Velocity download URL is replaced without changing the pinned build. A compression fix prevents forwarding released control frames.

Validation:

• Windows and Linux builds with JDK 25.
• Fresh mapping generation for all configured game versions produces no tracked changes.
• Fabric client/server play with encryption, world chunk delivery and multichannel, plus legacy registration and TCP checks.
• Minecraft 26.3 connections through Velocity and BungeeCord, plus compression and encryption regression checks.

Linux native transport was checked under WSL2. Encryption checks used local test identities, so online-mode account authentication remains untested. macOS native transport is also untested.

Addresses #82.