Add EU7 PACK v11 UTEX, section unload, and LRU streaming caches

Bake deduplicated section texture lists (UTEX) and read them at runtime so
texture warm/prefetch no longer scans every instance. Evict PACK sections
outside a 16 km keep ring and cap mesh/nodedata/texture warm caches to stop
RAM and apply cost from growing without bound during long fast camera flight.

- Bake v11 (format=4): UMES + UTEX + CHNK; mesh/texture ordering by frequency
- Runtime: incremental UTEX warm, adaptive apply slices, preempt/catchup tuning
- Unload: track instances per section, Region erase, pack pool release
- LRU: mesh/nodedata (2000, ref-counted), warmed textures (2048)
- Bench/diagnostics: unload and cache eviction counters
- Fix pack instance erase in Region; resolve duplicate helper symbols

rendering/particles.cpp

@@ -442,6 +442,23 @@ particle_manager::insert( std::string const &Sourcetemplate, TAnimModel const *N
     return true;
 }
 
+void
+particle_manager::erase_bound_node( TAnimModel const *const node ) {
+    if( node == nullptr ) {
+        return;
+    }
+
+    m_sources.erase(
+        std::remove_if(
+            std::begin( m_sources ),
+            std::end( m_sources ),
+            [node]( smoke_source const &source ) {
+                return source.m_ownertype == smoke_source::owner_type::node
+                    && source.m_owner.node == node;
+            } ),
+        std::end( m_sources ) );
+}
+
 // updates state of all owned emitters
 void
 particle_manager::update() {