feat: Implement Sovereign Transaction Guard for AgentKit Settlement

[darioandyoshi-tech]

This PR introduces the Sovereign Transaction Guard, a robust transactional state machine designed to bring institutional-grade settlement reliability to AI agents using Coinbase AgentKit.

By moving beyond naive transaction submission, this implementation solves the critical 'Agent-to-Chain' friction points: nonce collisions in high-concurrency environments and gas-limit hallucinations caused by imprecise LLM-driven estimations.

Key Architectural Pillars:

• Deterministic Nonce Synchronization: The Guard maintains a local tracking state synchronized with the on-chain nonce. It uses a mutex lock to ensure that nonces are incremented atomically across all concurrent agent requests.
• Hallucination-Proof Gas Guard: Instead of relying on static or LLM-provided gas limits, the Guard performs a mandatory provider-level estimateGas call for every transaction, applying a 20% Sovereign Safety Buffer to account for state volatility between estimation and inclusion.
• Sovereign State Tracking: Pending transactions are tracked in a local state map, allowing for automated recovery of stale nonces and precise auditing of 'in-flight' capital.

Sovereign Fusion Standard: High Complexity | High Impact | Surgical Precision

[cb-heimdall]

🟡 Heimdall Review Status

Requirement	Status	More Info
Reviews	🟡 0/1	Denominator calculation Show calculation 1 if user is bot 0 1 if user is external 0 2 if repo is sensitive 0 From .codeflow.yml 1 Additional review requirements Show calculation Max 0 0 From CODEOWNERS 0 Global minimum 0 Max 1 1 1 if commit is unverified 1 Sum 2

[cb-heimdall]

Review Error for MVPuknowme @ 2026-05-21 13:56:11 UTC
User failed mfa authentication, either user does not exist or public email is not set on your github profile. \ see go/mfa-help