Fix terrain streaming performance: revert copy back to move, remove broken cache

The previous commit changed std::move to copy for terrain/mesh data to fix
the empty-cache bug. But copying ~8 MB per tile × 81 tiles caused a 60s
streaming timeout.

The tile cache was already broken before — putCachedTile stored a shared_ptr
to the same PendingTile whose data was moved out, so cached tiles always had
empty meshes. Remove the putCachedTile call entirely; tiles re-parse from
ADT files (asset manager file cache hit) when they re-enter streaming range.

The softReset cache clear from the previous commit remains as safety for
map transitions.

src/rendering/terrain_manager.cpp

@@ -912,8 +912,8 @@ bool TerrainManager::advanceFinalization(FinalizingTile& ft) {
         // Commit tile to loadedTiles
         auto tile = std::make_unique<TerrainTile>();
         tile->coord = coord;
-        tile->terrain = pending->terrain;   // copy (not move) — pending is cached for reuse
-        tile->mesh = pending->mesh;           // copy (not move) — pending is cached for reuse
+        tile->terrain = std::move(pending->terrain);
+        tile->mesh = std::move(pending->mesh);
         tile->loaded = true;
         tile->m2InstanceIds = std::move(ft.m2InstanceIds);
         tile->wmoInstanceIds = std::move(ft.wmoInstanceIds);
@@ -921,7 +921,9 @@ bool TerrainManager::advanceFinalization(FinalizingTile& ft) {
         tile->doodadUniqueIds = std::move(ft.tileUniqueIds);
         getTileBounds(coord, tile->minX, tile->minY, tile->maxX, tile->maxY);
         loadedTiles[coord] = std::move(tile);
-        putCachedTile(pending);
+        // NOTE: Don't cache pending here — std::move above empties terrain/mesh,
+        // so the cached tile would have 0 valid chunks on reuse.  Tiles are
+        // re-parsed from ADT files (file-cache hit) when they re-enter range.
 
         // Now safe to remove from pendingTiles (tile is in loadedTiles)
         {