Fix Canvas player NPC region registration during spawn

[RLFrieren]

Canvas performs a region ownership check during ServerLevel#addFreshEntity. A Citizens player NPC reaches that call before its fake network connection is associated with the active RegionizedWorldData, so Canvas rejects the spawn as an async entity insertion.

The player is now positioned before insertion. On Canvas 26.1, the fake connection is attached to the active region only for the insertion operation, then removed in a finally block. The temporary view-distance change is restored there as well.

Validation:

• Canvas 26.1.2 build 876: repeated player NPC spawn, removal, death, and respawn cycles
• Folia 26.1.2 build 8: spawn and respawn smoke test
• mvn -DskipTests -pl v1_21_R7,v26_1_R1,v26_2_R1 -am compile

[CLAassistant]

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