Remove: TimeCurve launchpad docs/skills/bots; rewrite contributor guardrails

Context

Remove TimeCurve launchpad docs/skills/bots; rewrite contributor guardrails for TimeArena. Parent epic: #238 (closed).

Relevant files

• .cursor/skills/yieldomega-guardrails/SKILL.md
• skills/play-timecurve-doubloon/SKILL.md, play-active-timecurve/SKILL.md, play-timecurve-warbow/SKILL.md
• bots/timecurve/
• docs/frontend/timecurve-views.md, docs/qa/YO-TimeCurve-QA-Checklist.md
• docs/testing/invariants-and-business-logic.md — TimeCurve sections

Acceptance criteria

• New play skills: play-time-arena-doub, play-time-arena-warbow, play-active-time-arena
• Guardrails rewritten for Arena v2 (indexer invariants, Kumbaya DOUB paths, wallet modal)
• Bot swarm retargeted to TimeArena buys or removed with replacement plan

Verification checklist

• skills/README.md index updated
• Agent-phases Phase 20 references TimeArena not TimeCurve/Leprechaun/Rabbit