ship: use only the primary composite — fixes parts floating mid-ship

The sub-composites (`e_rou_<id>_eng`, `_wep_*`) are LOCAL detail rigs: their
nodes are posed in their own frame, not ship-space, so folding them in placed
the engines at ~mid-ship (Z≈99) instead of aft — the "floating in air" parts.

The PRIMARY composite (`e_rou_<id>`, the one with the most nodes) already carries
the full ship-space layout: every hull body AND every `GN_*` hardpoint frame
(GN_Bridge at the stern, GN_Engine aft, GN_ShieldG amidships…). Assemble from
that one composite only; engines/bridge/shield now resolve to their real aft/mid
frames. Robust to the odd single-composite case (e108's `e_rou_e108_Missile_open`
is still picked as its own primary).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

crates/sylpheed-formats/src/ship.rs

@@ -230,21 +230,38 @@ fn composites_for<'a>(names: &'a [String], id: &str) -> Vec<&'a String> {
 pub fn assemble_ship(bytes: &[u8], id: &str) -> Vec<ScenePart> {
     let names = xbg7_resource_names(bytes);
     let resources: HashSet<String> = names.iter().cloned().collect();
-    let comps = composites_for(&names, id);
+
+    // The PRIMARY composite carries the real ship-space layout (hull bodies +
+    // every `GN_*` hardpoint frame). Sibling composites (`e_rou_<id>_eng`,
+    // `_wep_*`) are LOCAL detail rigs — their nodes are in their own frame, not
+    // ship-space, so folding them in floats parts mid-ship. Pick the composite
+    // with the most nodes; that is the assembled hull.
+    let scenes: Vec<(String, Vec<ScenePart>)> = composites_for(&names, id)
+        .into_iter()
+        .map(|c| (c.clone(), scene_world_nodes(bytes, c)))
+        .collect();
+    let Some((_, nodes)) = scenes.iter().max_by_key(|(_, n)| n.len()) else {
+        // No composite at all → raw fallback below.
+        let mut placed = Vec::new();
+        const ID: [[f32; 3]; 3] = [[1.0, 0.0, 0.0], [0.0, 1.0, 0.0], [0.0, 0.0, 1.0]];
+        for part in names.iter().filter(|n| is_base_part(n) && ship_id_of(n) == Some(id)) {
+            placed.push(ScenePart { resource: part.clone(), m: ID, t: [0.0; 3] });
+        }
+        return placed;
+    };
 
     let mut placed: Vec<ScenePart> = Vec::new();
     let mut placed_res: HashSet<String> = HashSet::new();
-    // GN hardpoint frames, world-space, from every composite.
+    // GN hardpoint frames, world-space, from the primary composite.
     let mut frames: Vec<ScenePart> = Vec::new();
 
-    for c in comps {
+    for node in nodes {
-        for node in scene_world_nodes(bytes, c) {
         if node.resource.starts_with("GN_") {
-                frames.push(node);
+            frames.push(node.clone());
         } else if let Some(res) = resolve_hull_resource(&node.resource, &resources) {
-                // Only the ship's own parts. A composite also mounts shared,
+            // Only the ship's own parts. A composite also mounts shared, cross-id
-                // cross-id turret models (`e303_wep_*` on an `e106` hull); those
+            // turret models (`e303_wep_*` on an `e106` hull); those need the
-                // need the per-mount Vessel recipe and are placed separately.
+            // per-mount Vessel recipe and are placed separately.
             if ship_id_of(&res) != Some(id) {
                 continue;
             }
@@ -253,7 +270,6 @@ pub fn assemble_ship(bytes: &[u8], id: &str) -> Vec<ScenePart> {
             }
         }
     }
-    }
 
     // Place unplaced external parts at their Vessel hardpoint frame.
     const CATS: [(&str, &str); 3] = [("brg", "Bridge"), ("sld", "ShieldG"), ("eng", "Engine")];