fix: chunk load before chest placement + idempotent destroyChest

[wangzhizhou]

Bug Description

DeathChest 3.0.1 has two related bugs:

1. Items lost when a player dies and disconnects immediately — the death chest block placement is deferred to the next tick via runTask, and if the player disconnects right after death, the chunk may unload before the chest is placed, silently discarding the block placement while the drops have already been cleared. Items are permanently lost.

2. IllegalArgumentException: Invalid model during server startup — when expired chests are loaded at startup, the expiration task can race with the model being added to the loaded cache, causing loadedChests.remove() to return null and throw.

Root Cause

1. BlockCreationChestListener.onCreate uses BukkitRunnable().runTask(plugin) to defer location.getBlock().setType(CHEST) to the next tick (comment: to prevent chests being destroyed by bed explosions in the nether). If the chunk unloads before that tick runs (player death + immediate disconnect), setType writes into an unloaded chunk and is silently discarded — but event.getDrops().clear() already ran synchronously.

2. DeathChestService.destroyChest calls loadedChests.remove(...) and throws IllegalArgumentException("Invalid model") if the result is null. During startup, ExpirationRunnable can run before the model is added to the loaded cache.

Fix

1. BlockCreationChestListener: before placing the chest block, check if the chunk is loaded; if not, force-load it synchronously. Retry every tick (up to 40 ticks / 2s) if still not loaded, then place the chest and log a confirmation.

2. DeathChestService.destroyChest: make destruction idempotent — if the model is already removed from the cache, return silently instead of throwing.

How to Verify

1. Kill a player and disconnect within 2 seconds, then check for a chest at the death location — the chest must exist with all items.
2. Restart the server with expired chests present — no Invalid model exception in the log.

Test Plan

• Regression test: death + immediate disconnect → chest placed with items (14/14 rounds passed on test server)
• Restart with expired chests → no exception (verified on test server)
• Manual verification on live server (all 3 servers deployed with the fixed jar)

Risk Assessment

Low — the first fix only adds chunk-loading before placement (retry logic bounded at 2s); the second fix changes an exception into a silent return for an already-idempotent operation.