P0-04: Delete docs/superpowers, docs/PRD.md, docs/games, and two template docs #182

Part of #175 (audit Phase 0). Evidence: docs/audit/2026-11-09/detail/docs.md §1, §5, §6.

Why. docs/superpowers/ is 13 files / 4,328 lines (46% of all doc lines) of AI pair-programming plans, specs, and HTML mockups; all five features they describe are shipped and tested. docs/PRD.md is a May-2026 pre-festival snapshot nobody reads. docs/games/rhythm.md and upsidedown.md describe code deleted in May; bodycaptcha.md, bodygrid.md, keepaway.md are stale (hold "resets" vs drains, progress bar vs ring, wrong module path for BodyGridActivator, wrong update() signature). docs/agents/domain.md and docs/agents/triage-labels.md are unmodified third-party templates that reference files not in this repo.

Do.

git rm -r docs/superpowers docs/games docs/PRD.md docs/agents/domain.md docs/agents/triage-labels.md

• Salvage five one-liners into the Setup common.glsl headers (list in detail/docs.md §5: endless_sunset anti-goals, hunter_bird one-lock-one-strike, watering_can sideways-step-rewinds, rainbow_poop post-build revisions, and a sentence in shaders/README.md about modelling a new test_<setup>.py on an existing one).
• Fix inbound links: docs/FundingCAPTCHA.md:61 (four spec links) and docs/adr/0022-shader-player-blob-records.md (mockup link near the end).
• Fold the 5-line label table from triage-labels.md into docs/agents/git-workflow.md.
• Remove the docs/agents/domain.md link from AGENTS.md.
• If the UpsideDown/Rhythm port is still wanted, open one issue for it; otherwise nothing.

Done when. grep -r superpowers docs AGENTS.md is empty; no broken relative links under docs/; make test unchanged.