feat(bundles): Add base_sendBackrunBundle RPC

[cody-wang-cb]

Summary

Adds a new base_sendBackrunBundle RPC endpoint and in-memory store to enable backrun transactions to execute immediately after their target transactions during block building. Structured similarly to the resource metering API
#22

TIPS PR: base/tips#78

Changes

• New BackrunBundleStore:
  • Uses DashMap<TxHash, Vec<Vec<Recovered<OpTxEnvelope>>>> indexed by target tx hash
• New RPC method: base_sendBackrunBundle
  • Accepts Bundle format where:
    • txs[0] = target transaction (lookup key)
    • txs[1..] = backrun transactions (stored value)

Testing

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