feat(ingress-rpc): Add eth_sendBackrunBundle RPC method with op-rbuilder integration

[cody-wang-cb]

Summary

Adds a new eth_sendBackrunBundle RPC endpoint to the ingress service that validates, meters, and forwards backrun bundles to op-rbuilder

Changes

Configuration

• Added TIPS_INGRESS_BACKRUN_ENABLED flag to enable/disable backrun bundle submission

API

• New RPC method: eth_sendBackrunBundle
• Accepts standard Bundle format where:
  • txs[0] = target transaction (trigger)
  • txs[1..] = backrun transactions

Code Quality

• Refactored common bundle validation/parsing/metering into validate_parse_and_meter_bundle() helper
• Shared between send_bundle and send_backrun_bundle to reduce duplication

Testing

Added a new justfile util function send-txn-with-backrun to execute target tx + backrun bundles
From the logs
tips

2025-11-26T18:54:57.324826Z  INFO tips_ingress_rpc::service: sent transaction to the mempool hash=0xeb22037c2d5a7a2bf7e838264551307266090c5dd535637d43892211ad8d69e7
2025-11-26T18:54:57.437933Z  INFO tips_ingress_rpc::service: Validated and parsed backrun bundle bundle_hash=0xaefff145bf0161595de2d31eebea11c5c65ccb1d346f35c23c0ea2ee73d67ecd
2025-11-26T18:54:57.441090Z  INFO tips_ingress_rpc::service: Sent backrun bundle to op-rbuilder bundle_hash=0xaefff145bf0161595de2d31eebea11c5c65ccb1d346f35c23c0ea2ee73d67ecd builder_idx=0
2025-11-26T18:54:57.441135Z  INFO tips_ingress_rpc::service: Sent backrun bundle to audit channel bundle_hash=0xaefff145bf0161595de2d31eebea11c5c65ccb1d346f35c23c0ea2ee73d67ecd

op-rbuilder

2025-11-26T18:54:57.439472Z  WARN Received backrun bundle
2025-11-26T18:54:57.440797Z  WARN Parsed bundle
2025-11-26T18:54:57.440864Z  WARN Stored backrun bundle target_tx=0xeb22037c2d5a7a2bf7e838264551307266090c5dd535637d43892211ad8d69e7 backrun_tx_count=1
2025-11-26T18:54:57.440883Z  WARN Stored bundle
2025-11-26T18:54:58.028806Z  WARN Executing backrun bundles for transaction tx_hash=0xeb22037c2d5a7a2bf7e838264551307266090c5dd535637d43892211ad8d69e7
2025-11-26T18:54:58.028835Z  WARN Found backrun bundles for transaction target_tx=0xeb22037c2d5a7a2bf7e838264551307266090c5dd535637d43892211ad8d69e7 bundle_count=1

[wlawt]

qq: is there a difference between builder_tx and builder_clients?

[cody-wang-cb]

good point, i can merge the 2

[wlawt]

nit: is it possible to move all the helpers into the second impl here ?