Legacy old PvP

Fixes

• ViaVersion 5.12: sword blocking for 1.21.2+ clients through ViaVersion works again (5.12 moved one of its item classes).
• Full-charge hits with every weapon: a hit right after a swing no longer does about 88% damage with axes and swords.

Added

• Minecraft 26.3 support, tested on Paper 26.3.
• old-damage.debug (off by default) logs how each melee hit's damage is worked out.

Notes

• Item tooltips still show vanilla attack damage; actual hits use the 1.8 table. Tooltips are planned for 1.0.2.
• Folia has no 26.3 build yet.