Transmission #026: PDD planning for stats, achievements, and quests

Started a Prompt-Driven Development planning folder for comprehensive player stats, Carl-style achievements with trophy/lootbox rewards, inventory UI tabs (achievements + boxes), punch-to-open quest boards with autogenerated power-of-ten quests, and a path toward server-backed definitions. Artifacts live under .agents/planning/2026-04-22-stats-achievements-quests/ (rough-idea.md, idea-honing.md, and empty research/, design/, implementation/ for the rest of the PDD workflow).