Add Sub Rosa community skill

[karagozemin]

Summary

• list the Sub Rosa Agent Skill in the Community Skills catalog
• link directly to the public skill maintained with the Sub Rosa Core v2 SDK
• cover sealed-bid asset auctions, confidential proposal rounds, Drand reveal, SAC escrow and atomic settlement, lifecycle automation, receipts, and current testnet safety boundaries

Skill source

https://github.com/karagozemin/Sub-Rosa/blob/feat/core-v2/skills/sub-rosa/SKILL.md

Validation

• Agent Skills quick_validate.py: passed
• pnpm lint: passed
• pnpm lint:ts: passed
• pnpm build: passed
• verified the skill URL is publicly readable and the card appears in the static site and generated llms.txt

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