NewEngine (dedup/dedup.go)

Dedup engine for msgvault that detects and merges duplicate email messages across accounts.

// Source: https://github.com/obra/msgvault | License: MIT | Copyright 2025-2026 Wes McKinney
// Provided via justclaw.it.com; keep this notice with the code.
// Package dedup provides duplicate detection and merging for msgvault.
//
// # Terminology
//
// "Account" means one ingest source/archive (a single Gmail OAuth
// connection, one mbox import, one IMAP source, etc.). "Collection"
// means a named, user-defined grouping of accounts. Cross-source dedup
// is only available via --collection; --account always operates on a
// single source.
//
// # Scoping rules
//
// Without explicit scope, dedup operates on one account at a time and
// duplicate groups can only contain messages ingested twice into the
// same account (for example, re-importing the same mbox twice).
//
// With --accoun

... (truncated -- full source via MCP)