Add hardened key option to getPublicKeys

[Rigidity]

Note

Low Risk
Low risk: adds an optional boolean parameter to a WalletConnect command and threads it through to an existing getDerivations call, with a safe default of false. Main risk is minor compatibility issues if callers or backend expect different param shapes.

Overview
Adds an optional hardened flag to the WalletConnect chip0002_getPublicKeys command schema and forwards it to commands.getDerivations (defaulting to false). This lets callers request public keys derived from hardened paths without changing the command’s return shape.

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