docs: add troubleshooting section for MissingL1InfoDeposit error with pruned snapshots

[Kewe63]

Description

Adds a new troubleshooting subsection to the README covering the EngineReset(SyncStart(FromBlock(MissingL1InfoDeposit(...)))) error that users may encounter when syncing a Base node from a pruned snapshot that lacks sufficient historical data for consensus client initialization.

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Problem

Users syncing from an older pruned snapshot may experience a consensus client crash with a MissingL1InfoDeposit error for a specific block hash. Pruned snapshots discard historic state, and if the snapshot predates the early blocks required for deposit contract verification, the consensus client cannot complete initialization.

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Solution

The added subsection explains the root cause and provides clear, actionable remediation steps:

1. Check the block number associated with the snapshot to determine its age.
2. If the snapshot is older than ~40 days (approximately block 45,000,000 as of mid-2026), download a fresh snapshot from the official snapshots page.
3. Alternatively, delete the snapshot data directory and allow the node to sync from genesis — slower, but guarantees completeness.
4. Confirm that both execution and consensus clients point to the same data directory (/data by default).

An example command block for clearing data and restarting the node is included.

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Test Results

• Documentation-only change; no code or configuration is modified.
• New subsection renders correctly (verified locally via cat and visual inspection).
• No broken links or formatting issues introduced.
• Existing document structure and styling remain intact.

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Risk

None. This is a documentation addition only and has no effect on the node software, build process, or runtime behavior.

[cb-heimdall]

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