Use 26.3 tag for dangerous teleportation targets

### The Problem

We hardcode a list of blocks that we shouldn't teleport a user to. This is not mod-friendly.

### A Solution

26.3 provides a tag for this purpose. We should use it (and extend it if needed to maintain behavior).

### Alternatives

_No response_

### Anything Else?

_No response_

Start by locating the hardcoded list of blocks used to avoid dangerous teleportation targets and the code that handles teleportation. Check how the 26.3 tag is exposed in the relevant Minecraft integration, then verify that existing behavior remains unchanged while mod-defined tagged blocks are respected.

Written by the indexing model from the issue text.