Starknet Proposal Adds Standard Way to Discover Account Capabilities

Starknet Wallet API lacks account capability discovery, causing gasless accounts to fail. Proposal adds wallet_getCapabilities, a read-only method reporting execution mode, paymaster sponsorship, and session keys. Mirrors EIP-5792/ERC-7677. Additive, optional, backward-compatible. Wallets not implementing it default to self-broadcast and user-paid fees.