re(xbg7): a capture names a never-decoding family, and the cause is mixed strides in one pool

capture_ib_truth now proposes an identity for each drawn buffer our decoder cannot
place, by matching (vertex, index) counts against declared-but-not-decoded
resources. That identified n201_01/_02/_03 in Stage_S02.xpr — three of the 63
resources that decode in no container — and the capture pins all four sub-meshes:

  #0 vb 0x32BA71C ib 0x32B39FC 4464 idx 777 v stride 24
  #1 vb 0x32BEFF4 ib 0x32B5CDC 4464 idx 869 v stride 24
  #2 vb 0x32C416C ib 0x32B7FBC  576 idx 192 v stride 24
  #3 vb 0x32C536C ib 0x32B843C 4464 idx 869 v stride 28   <- different

The layout matches our assumptions exactly (tight index packing, last buffer flush
against vb0 so pad 0, span 27936 == align4-summed markers, contiguous vertex
buffers, max index == verts-1 everywhere). The defect is that sub-mesh #3 has a
different stride AND its own vertex shader: anchor_grouped_meshes parses one
declaration per resource and applies its stride to every sub-mesh, so it reads #3
out of phase (372 non-finite position components of 2607), and since the pivot is
the largest index count with ties going to the last marker, the pivot IS that
sub-mesh — so the whole resource is declined.

Also adds examples/miss_targets.rs (which container to aim a capture at): 63
resources decode nowhere, 58 of them in exactly one container, clustering as
Stage_S16 21 (e901_wing_05_*), ptc_pack 12, Base 6, then per-stage n2xx groups.
Flying stage 16 did not draw the e901 wings — the container is resident but the
unit must also be on screen.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NptfmpjdpNCKEez6d2xvA9

crates/sylpheed-formats/examples/grouped_report.rs

@@ -0,0 +1,2 @@
+fn main(){let a:Vec<String>=std::env::args().collect();let b=std::fs::read(&a[1]).unwrap();
+for l in sylpheed_formats::mesh::debug_grouped_report(&b,&a[2],a[3].parse().unwrap()){println!("{l}")}}