fix(mesh): refine the anchor map before using it -- inconsistency 63 -> 51

Pass 1's anchor map contains exactly the mistakes the neighbourhood is meant to
correct, so a resource sitting beside a mis-anchored neighbour inherits a bad
reference. Re-anchoring against the improving map and repeating converges
quickly: two rounds, and a third changes nothing (the loop exits early when a
round is a fixpoint).

  before                 decoded 5480/6294  inconsistent 125
  neighbourhood anchor   decoded 5480/6294  inconsistent  63
  + refining the map     decoded 5480/6294  inconsistent  51

Coverage still unchanged. The 51 that remain cluster in _l (LOD) and _dead
variants -- e001_l, e010_bdy_01_l, e106_eng_02_l, _rou_f302_base_dead,
e303_base_dead and friends. A plausible reading is that a variant shares its
base's vertex and index counts, making the two mutually confusable so that
locality cannot separate them; recorded as untested rather than asserted.

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

crates/sylpheed-formats/src/mesh.rs

@@ -653,7 +653,25 @@ impl Xbg7Model {
         let pass1: Vec<(Option<Xbg7Model>, Option<usize>)> =
             resources.iter().enumerate().map(run1).collect();
 
-        let vbs: Vec<Option<usize>> = pass1.iter().map(|(_, vb)| *vb).collect();
+        let mut vbs: Vec<Option<usize>> = pass1.iter().map(|(_, vb)| *vb).collect();
+
+        // Refine the anchor map before using it: pass 1's anchors include the
+        // very mistakes this is meant to correct, so a resource next to a
+        // mis-anchored neighbour inherits a bad reference. Re-anchoring against
+        // the improving map and repeating converges quickly; two rounds is
+        // enough on this disc (a third changes nothing).
+        for _ in 0..2 {
+            let refined: Vec<Option<usize>> = (0..resources.len())
+                .map(|i| match (need_pass1[i], neighbourhood(&vbs, i)) {
+                    (true, Some(anchor)) => decode_one_near(&resources[i], Some(anchor)).1.or(vbs[i]),
+                    _ => vbs[i],
+                })
+                .collect();
+            if refined == vbs {
+                break;
+            }
+            vbs = refined;
+        }
 
         // Pass 2 — re-anchor preferring the resource's own neighbourhood, which
         // is what separates its data from another resource's identically-shaped

crates/sylpheed-formats/tests/mesh_consistency_disc.rs

@@ -53,7 +53,7 @@ fn span(m: &Xbg7Model) -> Option<[i64; 3]> {
 }
 
 #[test]
-#[ignore = "known-failing: 63 of 681 shared resources still decode inconsistently (was 125 before the neighbourhood anchor, 2026-08-12)"]
+#[ignore = "known-failing: 51 of 681 shared resources still decode inconsistently (125 before the neighbourhood anchor, 63 before refining it — 2026-08-12)"]
 fn shared_resources_decode_identically_in_every_container() {
     let Some(root) = disc_root() else {
         eprintln!("SKIP: extracted disc not found (set SYLPHEED_DISC to enable)");