re: exact anchor offsets (GameMesh.vbuf_offset) -- correcting yesterday's defect table

The first read of the capture-truth table located our resources by searching the
container for their leading vertices, which reads much worse than reality: the
same leading run occurs at several offsets in one container. GameMesh now carries
the offset the anchor scan actually chose, so the comparison is exact -- 4 of the
ship's drawn buffers are anchored correctly, 2 are the twin collapse, and 2 are
real mis-anchors of a size we do decode (brg 51 verts, eng_02_l 44).

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

crates/sylpheed-viewer/src/iso_loader.rs

@@ -3677,6 +3677,7 @@ fn exhaust_cone_mesh() -> sylpheed_formats::mesh::GameMesh {
         uvs: Vec::new(),
         indices,
         name: Some("exhaust".to_string()),
+        vbuf_offset: None, // procedural, not read from a container
     }
 }