Tests: rpc initial setup and rpc tests phase 1

[kollegian]

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Testing performed to validate your change

[cursor]

PR Summary

Low Risk
Adds integration tests and CI wiring only; no production RPC or node logic changes.

Overview
Adds a self-contained integration_test/rpc_tests module that compares Sei’s EVM JSON-RPC to a local geth --dev reference (happy path, schema, empty/null handling, and byte-for-byte error parity via raw JSON-RPC). A one-time bootstrap deploys shared fixtures (TestERC20, gas burner, EIP-7702 target), mirrors ERC20 on geth, pre-funds a signer pool, and writes runtime/runtime.json for parallel Mocha specs under eth/.

CI: New integration matrix job “EVM RPC Parity (geth reference)” runs scripts/run-ci.sh (GIGA_STORAGE=true); workflow always uploads the merged mochawesome report from reports/merged (ignores if missing).

Phase 1 specs cover core eth_* methods (accounts, block number/hash, chain id, coinbase, call, estimateGas, feeHistory, gasPrice, getBalance, getBlockByNumber/Hash), including Sei-only behavior (precompiles, sei_* helpers) and documented divergences from geth where intentional.

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The latest Buf updates on your PR. Results from workflow Buf / buf (pull_request).

Build	Format	Lint	Breaking	Updated (UTC)
✅ passed	✅ passed	✅ passed	✅ passed	Jun 3, 2026, 12:44 PM

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 58.17%. Comparing base (2151ba0) to head (699aa8d).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3520      +/-   ##
==========================================
- Coverage   59.12%   58.17%   -0.96%     
==========================================
  Files        2213     2129      -84     
  Lines      182814   173668    -9146     
==========================================
- Hits       108096   101035    -7061     
+ Misses      64993    63643    -1350     
+ Partials     9725     8990     -735     

Flag	Coverage Δ
sei-db	70.41% <ø> (ø)
sei-db-state-db	?

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[cursor]

Cursor Bugbot has reviewed your changes using default effort and found 1 potential issue.

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