v4.1.1

Upgrade priority: Low. Recommended when tracking the latest updates from Substrate.

Changes:

• Fix author extraction for last block in a session
• Expand SignerPayload to inject/expose custom signed extensions
• ConsensusEngineId formats non-Ascii engines correctly
• Allow getBlock/Header derives to use as-at registry (instead of latest)
• Cleanup RpcCore augmentation (removing TS warnings on typegen chains)
• Add upgrade block for Kusama 2029
• Ensure that type alias overrides also apply to map keys
• Check type generation against fallbacks (build-time only sanity check)
• Add mmr_generateProof RPC
• Align types with latest substrate master
• Apply latest Polkadot auctions/crowdloan/parachains/slots types