feat(spec-tests): validate transaction test fixtures against EELS

[danceratopz]

Description

Transaction test fixtures were generated but not exercised by the repository's JSON loader. That left their raw transaction bytes and expected results unchecked against EELS.

This PR adds a fork-aware adapter that decodes each raw transaction and uses EELS to validate its chain ID, signature, and state-independent transaction rules. It compares the resulting exception, transaction hash, sender, and intrinsic gas with the fixture. The JSON loader now discovers transaction fixtures from both checked-in files and filler output.

The adapter uses the common validate_transaction(transaction) interface introduced by the first PR in this stack. It does not duplicate fork validation rules.

Stack

This is the final PR in a three-PR stack:

1. feat(spec-specs): expose state-independent transaction validation #3492 — Expose state-independent transaction validation.
2. feat(test-fixtures): resolve implicit transaction test gas limits #3493 — Resolve implicit transaction test gas limits.
3. feat(spec-tests): validate transaction test fixtures against EELS #3494 — Validate transaction test fixtures with EELS (this PR).

Related Issues or PRs

Follows #3156, which added the transaction tests and fixtures this loader validates.

Testing

• Added focused coverage for valid and invalid fixtures across supported forks.
• Verified fixture discovery from JSON loader inputs and filler output.
• just static at each commit boundary.
• just test-tests at each commit boundary.

Checklist

• Ran fast static checks to avoid CI fails, see Code Standards and Verifying Changes: just static
• PR title has the form <type>(<area>): <title>, where <type> and <area> match the applied labels.

Cute Animal Picture

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.01%. Comparing base (73023cf) to head (0a64bab).

Additional details and impacted files

@@                                 Coverage Diff                                 @@
##           experiments/resolve-implicit-tx-test-gas-limits    #3494      +/-   ##
===================================================================================
+ Coverage                                            93.90%   94.01%   +0.10%     
===================================================================================
  Files                                                  624      624              
  Lines                                                36938    36938              
  Branches                                              3330     3330              
===================================================================================
+ Hits                                                 34688    34728      +40     
+ Misses                                                1569     1534      -35     
+ Partials                                               681      676       -5     

Flag	Coverage Δ
unittests	94.01% <ø> (+0.10%)	⬆️

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