fix: handle dynamic ephemery genesis metadata across config and lightclient paths

[shrirajpawar4]

Motivation

Ephemery was added in #6054, but some paths still assumed its genesis metadata was static. That left the remaining issue from #6050 unresolved in places that depend on genesisValidatorsRoot, fork
digests, and reset-aware chain config values.

Description

This PR completes the remaining Ephemery work by treating its network metadata as runtime-derived instead of fully static.

Changes included:

• derive Ephemery MIN_GENESIS_TIME, DEPOSIT_CHAIN_ID, and DEPOSIT_NETWORK_ID from the current reset iteration
• mark Ephemery genesisValidatorsRoot as unknown (null) in static network metadata
• update validator slashing protection to fetch genesisValidatorsRoot from the beacon API when static metadata does not provide one
• preserve an already-built runtime BeaconConfig in lightclient route serialization so fork digests use the correct live genesis context
• add regression tests covering:
  • dynamic Ephemery config values
  • nullable Ephemery genesis metadata
  • slashing protection fallback behavior
  • lightclient serialization with runtime Ephemery config
• add one explicit mainnet null check in validator tests to account for the new nullable genesisValidatorsRoot type

Closes #6050

AI Assistance Disclosure

• External Contributors: I have read the contributor guidelines and disclosed my usage of AI below.

used Codex to understand the code structure and identify the remaining gaps related to this issue. Each change was reviewed and is understood by me.

[gemini-code-assist]

Code Review

This pull request refactors the Ephemery network configuration to support dynamic genesis and periodic resets. Key changes include updating the GenesisData type to allow a null genesisValidatorsRoot, implementing derivation functions for Ephemery's chain configuration based on the current time, and updating the API and CLI utilities to handle runtime-defined beacon configurations. These updates ensure correct light client serialization and slashing protection for networks where the genesis root is not statically known. I have no feedback to provide.

[chatgpt-codex-connector]

💡 Codex Review

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Reviewed commit: ddf61d657b

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[nflaig]

@shrirajpawar4 please address the AI review comments

[shrirajpawar4]

@nflaig done ser. The genesis fetch call is now inside the try block, so --force falls back to the zero root when api.beacon.getGenesis() throws before assertOk() is reached.