feat(docs): add guide for deriving Lit Action public keys

[Ansonhkg]

WHAT

Add a new guide section for the docs

[Copilot]

Pull Request Overview

This PR introduces a new guide section to the documentation that explains how to deterministically derive Lit Action public keys without executing the action externally. The guide demonstrates using Lit.Actions.getActionPublicKey and Lit.Actions.signAsAction to work with action identities derived from IPFS CIDs.

Key Changes

• Added comprehensive documentation for deriving Lit Action public keys locally
• Included complete code example showing signature generation, key derivation, and verification
• Integrated new guide into the documentation navigation structure

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
docs/guides/lit-action-sign-as-action.mdx	New guide document explaining the complete workflow for deriving and verifying Lit Action public keys with code examples
docs/docs.json	Updated navigation structure to include new "Guides" section with reference to the new guide

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[Copilot]

The question describes obtaining the public key 'outside of the Action runtime' and 'locally without running the Action', but the answer demonstrates deriving the key from within the Action context. This creates confusion about whether the solution actually addresses the stated problem of getting the key without executing the Action.

[Copilot]

The comment states 'derive it from the Action IPFS CID', but the code doesn't demonstrate deriving anything at this line. The derivation happens later at line 43. This comment could mislead readers about where the derivation actually occurs.

Suggested change

	const { sigName, toSign } = jsParams; // 'publicKey' not required; derive it from the Action IPFS CID
	const { sigName, toSign } = jsParams; // 'publicKey' not required in jsParams; it will be derived later from the Action IPFS CID