remove spectrum

[HashimTheArab]

Note

Medium Risk
Medium risk: introduces new connection-swapping logic (TryTransfer) with packet ID translation and state resets, which can affect gameplay/network correctness during transfers; also bumps core networking deps (gophertunnel, go-raknet).

Overview
Removes Spectrum support entirely (deletes spectrum.go and example/spectrum, trims README dependencies, drops Spectrum/legacy-version modules) and updates .gitignore accordingly.

Adds fast upstream transfer support: the player now handles server Transfer packets by dialing a new upstream connection (TryTransfer), swapping ServerConn, invalidating ACKs, and clearing client-visible state (chunks/entities/bossbars/player list/objectives/effects/weather) before resyncing basic gamemode/rules/position and chunk radius.

Implements transfer-safe entity ID handling by tracking client vs server runtime/unique IDs (ClientRuntimeId, ClientUniqueId, IDModified) and translating relevant client/server packets during transfers; also adds World.ChunkPositions() and WorldUpdaterComponent.ResetForTransfer() to reset stale world-updater state.

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Cursor Bugbot has reviewed your changes and found 1 potential issue.

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NetworkChunkPublisherUpdate position uses chunk coordinates instead of block

High Severity

The NetworkChunkPublisherUpdate.Position field is a protocol.BlockPos and expects block coordinates, but the >> 4 shift converts block coordinates to chunk coordinates. For a player at X=100, Z=200, the position would incorrectly be set to (6, 0, 12) instead of (100, 0, 200). This means after a fast transfer, the chunk publisher center would be far from the player's actual position, preventing chunks from loading around them.