docs: archive Fellowship Reading Room handoff

[WalksWithASwagger]

Summary

• document the five approved AI Builders Fellowship launch assets and three selected Reading Room variations
• record dimensions, SHA-256 receipts, archive and brand provenance, preserved hard-gate rejections, and local recovery paths
• preserve the repository public boundary: prompts, reference media, provider receipts, and generated outputs remain local and gitignored
• record the live GitHub overlap check and adjacent model-evaluation work

Verification

• ./.venv/bin/python prompts/bcai-fellowship-2026-07/verify-reading-room.py
• ./.venv/bin/python prompts/bcai-fellowship-2026-07/variations-r2/verify-variations-r2.py
• npm run docs:check
• npm run public:check
• npm run env:audit
• npm run env:scan
• git diff --cached --check

All checks passed. No provider call, image commit, website integration, deployment, or publication is included.

Related work

No open issue or PR directly names this Fellowship campaign. Issues #335 and #336 are adjacent model-evaluation work but do not block this documentation handoff.