FEATURE: Transfurred ability and attribute progression tree. [OPEN FOR COMMENT]

Transfurred players have access to a progression tree (mostly) unique to their variant. This adds a long-term commitment and objective to accomplish after being transfurred.

Players can unlock the next node connected to an already unlocked node to obtain one of the following:

• Attribute upgrade [Through the attribute system]
  • Max health
  • Movement speed
  • Swim speed
  • "Armor"
• Property upgrade [TransfurVariant<?> properties]
  • Jump strength
  • Breathe mode
  • Step size
  • Jump charges [Bee, moth]
  • Mining strength
• Transfur buff upgrade [Upon transfurring an entity]
  • Bonus healing
  • Bonus strength (strength, duration)
  • Bonus haste (strength, duration)
• Ability unlock
  • Create item ability
  • Wave vision ability
  • Summon sharks ability
• Ability upgrade
  • Ability cooldown/recharge
  • Ability effectiveness

Considerations must be made upon certain events that would change the player's transfur variant (i.e. Changing gender, respawning & retransfurring, other mod processes), and what to do with the unlocked nodes on the new variant.

Trees for each variant can be defined in a datapack for server/modpack/mod customization.

The trees can be rendered in one of the two (or other) following ways:

Both the trees drawn here represent the same underlying tree with the same nodes.
Each node would have an icon, name, description, and cost/requirements.

Cost/requirements could be a factor of components, and can pair with vanilla progression:

• Time spent transfurred (total/as variant)
• Number of entities transfurred (Weighted across entities, such that players and villagers are worth more than zombies and skeletons)
• Vanilla and modded advancements
• Player XP (Present the choice of enchanting equipment OR upgrading their transfur).

No files, tests, or entry points are named. Start by resolving the progression-tree design, including TransfurVariant<?> changes, variant-change behavior, datapack definitions, and rendering requirements. Done means the scope, node rules, persistence behavior, and implementation entry points are agreed.