Implement Emergency Pause Mechanism for TestArbitrage Contract

[Neros0]

Summary

This PR adds critical emergency pause functionality to the TestArbitrage contract, allowing the contract owner to temporarily halt operations in emergency situations and resume them when safe.

Changes

New Event

• EmergencyAction: Emitted during emergency operations to provide comprehensive audit trail
  • Tracks the action type (e.g., "contract_paused", "contract_unpaused")
  • Records the token address if applicable (uses address(0) for pause operations)
  • Logs the amount involved if applicable (uses 0 for pause operations)
  • Captures the executor's address for accountability

New Functions

pause()

• Access: Owner only
• Functionality: Immediately pauses all contract operations
• Use Case: Emergency situations requiring immediate intervention (e.g., detected exploit, oracle manipulation, market anomalies)
• Implementation: Leverages OpenZeppelin's Pausable._pause() for standardized behavior
• Emits: EmergencyAction event with action type "contract_paused"

unpause()

• Access: Owner only
• Functionality: Restores normal contract operations
• Use Case: Resume operations after emergency has been resolved
• Implementation: Uses OpenZeppelin's Pausable._unpause() for state management
• Emits: EmergencyAction event with action type "contract_unpaused"

Technical Details

• +22 lines added to src/onchain/TestArbitrage.sol
• Utilizes existing Ownable and Pausable inheritance
• No breaking changes to existing functionality
• Event-driven design for transparency and monitoring

Security Considerations

• Both functions are protected by onlyOwner modifier
• Uses battle-tested OpenZeppelin Pausable implementation
• All emergency actions are logged via events for off-chain monitoring
• No state changes beyond pause status to minimize attack surface

Documentation

All functions and events include comprehensive NatSpec comments explaining:

• Purpose and use cases
• Implementation details
• Access control requirements

Testing Recommendations

Before merging, ensure the following scenarios are tested:

1. Only owner can call pause() and unpause()
2. Non-owner calls revert with appropriate error
3. Events are emitted correctly with expected parameters
4. Paused state prevents flashloan execution and other critical operations
5. Unpause successfully restores functionality
6. Cannot pause when already paused (if desired behavior)
7. Cannot unpause when not paused (if desired behavior)

Related Issues

Add any related issue numbers or emergency incident tickets