Add AI citation notes to one protocol lesson

[beihaili]

Context

AI agents work better when lessons have clear source context and stable citations for protocol facts.

Expected files

Pick one lesson with protocol or security claims, for example under:

• en/GetStartedWithBitcoin/
• en/EthereumSmartAccounts/
• en/DeFiDeepDive/
• corresponding zh/ lesson paths

Generated artifacts may also change:

• ai/content-index.json
• ai/llms.txt
• ai/manifest.json
• public/ai/*

Acceptance criteria

• Add a short Further reading, Sources, or citation note section to one lesson.
• Use official docs, standards, specs, or reputable explainers.
• Keep the added section concise and beginner-readable.
• Regenerate AI artifacts if indexed content changes.

Definition of done

The selected lesson is easier for both learners and AI agents to cite accurately.

Verification

• Run npm run ai:index && npm run ai:publish && npm run ai:verify.
• Run npx prettier --check <changed-markdown-file>.

Good first issue candidate: yes.

[scosemicolon]

A concise source block would fit well in the Taproot lesson because it already has several exact protocol claims that AI agents may quote later.

Candidate section:

## Further Reading

- BIP340: Schnorr Signatures for secp256k1, for the fixed 64-byte signature format and verification rules.
- BIP341: Taproot, for the key-path/script-path spending model and activation details.
- BIP342: Validation of Taproot Scripts, for Tapscript behavior and script-versioning context.
- Bitcoin Core 22.0 release notes, for user-facing Taproot wallet/node support context.

That would give learners and llms.txt consumers stable primary sources without making the lesson heavier.