Tracked generated content ownership

- Generated furniture keeps ownership tokens for targeted removal
- Native writes invalidate pending custom content and tile records
- Regeneration and chunk updates remove invalidated content on owning threads
- Provider callbacks return ownership tokens across server platforms
- Regression fixtures cover terrain replacement and restart cleanup

adapters/modded-common/src/versions/1.21.1/test/source-replacements.json

@@ -136,6 +136,12 @@
         "replacement": "when(level.getMaxBuildHeight()).thenReturn(320);"
       }
     ],
+    "art/arcane/iris/modded/api/ModdedCustomContentRegistryTest.java": [
+      {
+        "pattern": "\\bResourceLocation\\b",
+        "replacement": "Identifier"
+      }
+    ],
     "art/arcane/iris/modded/service/ModdedChunkUpdateServiceCarrierTest.java": [
       {
         "pattern": "\\bResourceLocation\\b",