re: CORRECTION -- the static assembler is not at fault, the pre-fix decoder was

Last iteration reported e303_wep_01 as inflated 30-110x by assemble_ship. Wrong:
the composite nodes carry scale 1.0 and orthonormal matrices, and under the
current decoder the turret places as 49x23x42 at +/-179. The 1600x2100x4800 box
only appears with XBG7_COVER_SLACK=4 -- the exact-coverage fix had already
repaired the turret too. The error came from comparing a deliberately pre-fix
render against post-fix measurements.

The containment screen's blindness therefore has a mundane cause: one mis-decode
inflated the envelope and hid another. Kept as a forward-looking invariant with
that caveat.

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

crates/sylpheed-formats/examples/filter_consistency.rs

@@ -0,0 +1,35 @@
+//! Does a FILTERED decode agree with the full one?
+//!
+//! Distinct anchor assignment resolves collisions against the set of resources
+//! being decoded — so `models_named` (a filtered subset, used by the ship
+//! assembler and the viewer) can reach a different answer from a whole-container
+//! decode. This measures that directly.
+//! Usage: filter_consistency <container.xpr> [resource...]
+use sylpheed_formats::mesh::Xbg7Model;
+use std::collections::HashSet;
+fn main() {
+    let a: Vec<String> = std::env::args().collect();
+    let bytes = std::fs::read(&a[1]).expect("container");
+    let full = Xbg7Model::anchor_models_cancellable(&bytes, 0.0, &|| false);
+    let names: Vec<String> = if a.len() > 2 {
+        a[2..].to_vec()
+    } else {
+        full.iter().map(|m| m.name.clone()).collect()
+    };
+    let mut differ = 0usize;
+    for n in &names {
+        let want: HashSet<String> = std::iter::once(n.clone()).collect();
+        let one = Xbg7Model::models_named(&bytes, &want, &|| false);
+        let (Some(f), Some(s)) = (full.iter().find(|m| &m.name == n), one.first()) else {
+            continue;
+        };
+        let off = |m: &Xbg7Model| m.meshes.first().and_then(|s| s.vbuf_offset).unwrap_or(0);
+        if off(f) != off(s) {
+            differ += 1;
+            if differ <= 10 {
+                println!("{n}: full decode at 0x{:x}, filtered at 0x{:x}", off(f), off(s));
+            }
+        }
+    }
+    println!("{differ} of {} resources decode differently when filtered", names.len());
+}

crates/sylpheed-formats/examples/node_scale.rs

@@ -0,0 +1,20 @@
+//! Dump a composite's scene nodes with their scale — the transform the static
+//! assembler copies verbatim into a placement.
+//! Usage: node_scale <container.xpr> <composite name>
+use sylpheed_formats::mesh::scene_world_nodes;
+fn main() {
+    let a: Vec<String> = std::env::args().collect();
+    let bytes = std::fs::read(&a[1]).expect("container");
+    for n in scene_world_nodes(&bytes, &a[2]) {
+        // Row norms of `m`: a rotation has all three at 1.0; anything else is a
+        // scale baked into the matrix, which `s` does not show.
+        let norm = |r: [f32; 3]| (r[0] * r[0] + r[1] * r[1] + r[2] * r[2]).sqrt();
+        println!(
+            "{:<26} s[{:7.3}{:7.3}{:7.3}]  |m rows|[{:7.3}{:7.3}{:7.3}]  t[{:9.1}{:9.1}{:9.1}]",
+            n.resource,
+            n.s[0], n.s[1], n.s[2],
+            norm(n.m[0]), norm(n.m[1]), norm(n.m[2]),
+            n.t[0], n.t[1], n.t[2]
+        );
+    }
+}