feat: add optional details field to Transaction type

[danroc]

Description

This PR adds an optional details field to the Transaction type to support transaction origin tracking and security alert responses.

Current State

The Transaction type currently lacks fields to track:

• Where a transaction originated (MetaMask internally or a dapp)
• Security assessment results from the Security Alert API

Solution

Adds an optional details object containing:

• origin (optional string): Transaction request source (e.g., 'metamask' or dapp URL)
• securityAlertResponse (optional enum): Security Alert API response (benign, warning, malicious)

The implementation is backward compatibile.

Examples

N/A - This is an API enhancement that consumers can adopt incrementally.

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Note

Adds optional context to transactions while preserving backward compatibility.

• Introduces Transaction.details (optional) with origin and securityAlertResponse
• Adds SecurityAlertResponse enum (benign, warning, malicious) and TransactionDetailsStruct using exactOptional
• Updates TransactionStruct to include details; type tests in transaction.test-d.ts and runtime validation tests in transaction.test.ts
• Changelog updated

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