fix(protocol/derive): fix singular batch extraction error handling

[sebastianst]

This is the same fix as ethereum-optimism/optimism#18283 for Kona.

Fixed for the post-Holocene BatchValidator and old BatchQueue. Unit tests added.

The derivation rule was technically in the specs already, but they get clarified with ethereum-optimism/specs#863.

[codecov]

Codecov Report

❌ Patch coverage is 97.77778% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 84.3%. Comparing base (e800861) to head (437c084).
⚠️ Report is 2 commits behind head on main.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
crates/protocol/protocol/src/batch/span.rs	96.6%	5 Missing ⚠️

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[Copilot]

Pull request overview

This PR fixes singular batch extraction error handling in the protocol derivation pipeline for post-Holocene batch validation. It addresses a scenario where overlapping span batches can pass prefix checks but contain batches with outdated L1 origins after the safe head. When such invalid batches are detected during extraction, the stage is now properly flushed and the error is handled consistently with dropped batches during prefix checks.

Key Changes:

• Added validation check to detect and reject batches with L1 origins before the safe head L1 origin
• Improved error handling in BatchStream to flush the stage when singular batch extraction fails
• Refactored batch validation logic with clearer variable naming (batch_timestamp, batch_epoch)

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 4 comments.

File	Description
crates/protocol/protocol/src/batch/errors.rs	Adds L1OriginBeforeSafeHead error variant for detecting outdated batch origins
crates/protocol/protocol/src/batch/span.rs	Implements validation check in both get_singular_batches and check_batch methods, improves variable naming consistency, adds comprehensive test coverage
crates/protocol/derive/src/stages/batch/batch_stream.rs	Updates error handling to properly catch extraction failures, flush the stage, and propagate errors; consolidates metrics code under feature flag

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[theochap]

@sebastianst there are still a couple of tests failing. Can we fix those before we merge this PR?

[theochap]

It seems that CI is stuck for this one. I am going to force merge it. I need to get this in asap