QuestLog Envelope Addon [QLXE]

Changed

• Letters and package pages rewarded together to the same player now share one Envelope courier. Each delivered item keeps its own contents, quest marker, signature and circle actions.
• Cargo is persisted during transport. Partial delivery retries only remaining items; stale courier references cannot replay a completed lot. Mailbox overflow drops beside the mailbox.
• Lots containing packages use express delivery; letter-only lots retain normal Envelope timing.

Validation

• 54 common tests cover mail progression, cargo persistence, partial delivery, retries, stale references and quest progress reset.
• Fabric LAN testing reported intact contents and no pigeon spawn lag. The local circle smoke fixture now uses an objective to prevent Questlog's empty-objective completion notice after reset.
• Both loader builds are checked. Grouped-delivery gameplay on NeoForge, mailbox overflow and restart during transport remain unconfirmed in game.