feat: support dynamic Summit epochs and checkpoint chains

[matthias-wright]

Changes:

• Switched Summit integration to getLatestCheckpointInfo and getEpochBounds RPCs.
• Updated snapshot archives to include Summit verification artifacts.
• Added dynamic checkpoint scheduling with correct Reth unwind and delay blocks.
• Added startup checkpoint recovery and state/disk reconciliation.
• Added persistent finalized-header caching and contiguous verification-header bundles.
• Standardized local and downloaded snapshots on epoch_N/epoch_N.tar.gz with atomic publication.
• Added configurable Summit RPC timeouts and handling for Summit’s “checkpoint not found” response.
• Added snapshot retention validation and configurable output-directory support for the RPC server.
• Removed unused Summit types, SSZ, and Commonware dependencies.