Integrate stats, resources, and cosmetics into adventures via conditional
branches gated by game state checks. Each of the 9 adventures now has a
secret branch that rewards exploration and encourages replay with subtle
hints on locked choices. The endgame box now triggers a Destiny adventure
that acknowledges all completed adventures and secret branches, with four
ending tiers culminating in an ultimate ending when all 9 secrets are found.
Also adds the crafting engine, CLAUDE.md and specifications.md for faster
onboarding.