ship: index-less brg/eng/sld parts never matched their GN frame — 34 ships assembled without a bridge

Tier 3 matched a part to its hardpoint by trailing index, so `e105_brg`
compared "01" == "" against GN_Bridge_01 and fell through silently. The runtime
capture is what exposed it: the game draws the bridge and places it at
[0, 70, -1850] rel e105_bdy_01, and assemble_ship emitted nothing there.

With no index to match on, take the lowest-numbered frame of the category.
Diffing assemble_ship part counts across every container: 34 (stage, ship)
entries gain parts — e102 +2 (bridge and engine), e104 +1, e105 +1, Stages
02-29. ship_audit is unchanged, so nothing regressed, and the capture now agrees
to dT 0.03 / dR 0.000.

Also fixes the diff itself: correlate_frames compared static against a rotation
sampled from the first block, which can belong to another INSTANCE of the class.
Scoped to the position-agreeing cluster, e105_eng_01 goes 1.711 -> 0.000 and
both e106 nacelles to 0.000. The one remaining rotation delta (e106_wep_02_01,
0.134) is a turret whose rotation varies by 0.182 between blocks that agree on
its position — the runtime disagrees with itself more than with the assembler.
The new rotVar column makes that distinction visible.

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

crates/sylpheed-formats/src/ship.rs

@@ -349,9 +349,21 @@ pub fn assemble_ship(bytes: &[u8], id: &str, include_external: bool) -> Vec<Scen
         let Some((_, gncat)) = CATS.iter().find(|(c, _)| *c == cat) else {
             continue;
         };
-        if let Some(frame) =
-            frames.iter().find(|f| f.resource.contains(gncat) && trailing_index(&f.resource) == idx)
-        {
+        // An index-less part (`e105_brg`, against a `GN_Bridge_01` frame) used to
+        // compare `"01" == ""` and fall through, so the bridge was silently
+        // dropped from the assembly while the game draws it — caught by a runtime
+        // capture, which places `e105_brg` at the `GN_Bridge_01` frame exactly.
+        // With no index to match on, take the lowest-numbered frame of the
+        // category; an indexed part still matches its own index only.
+        let mut cands: Vec<&ScenePart> = frames
+            .iter()
+            .filter(|f| {
+                f.resource.contains(gncat)
+                    && (idx.is_empty() || trailing_index(&f.resource) == idx)
+            })
+            .collect();
+        cands.sort_by_key(|f| trailing_index(&f.resource).parse::<u32>().unwrap_or(u32::MAX));
+        if let Some(frame) = cands.first().copied() {
             placed.push(ScenePart { resource: part.clone(), m: frame.m, t: frame.t, s: frame.s });
             placed_res.insert(part.clone());
         }