research: headroom-only landings, band fit, bore exemption (L156; last landing round, kept as patch)

Band fit works (all chambers inside host bands, 16/16 seeds both sweeps); chamber support exemption + open-floor
control work; found a metres/subvoxel mix in the shell-opening predicate. Still fails: upper landing evaluated grade
22.85 deg over native ground; TN and VS sweeps 0/16; UE 30 m/s near coverage 39.0% vs 45.5%. Owner: stop forcing
landings after this round.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016dhxM43dnWvUu2B5Ph1iG1

Standalone/Research/WorldAssemblerM3/Linux156/captures/INDEX.md

@@ -0,0 +1,35 @@
+# L156 matched owner tunnel landing captures
+
+Seed 0 camera poses resolved from the L156 owner layout and reused for both versions. Each view is at eye height at one of the three tunnel landing chambers. Before uses the L151 head build; after uses L156 source stamp `4bf096c0a06f72eb765ff8785d55c00ded946ed1bd1f39fa1914b3658ceb61f0`.
+
+## passage/0-1/0 / upper landing
+
+- Before: [image](before-l151-0-1-0-upper-landing.jpg)
+- After: [image](after-l156-0-1-0-upper-landing.jpg)
+
+## passage/0-1/0 / lower landing
+
+- Before: [image](before-l151-0-1-0-lower-landing.jpg)
+- After: [image](after-l156-0-1-0-lower-landing.jpg)
+
+## passage/1-2/0 / upper landing
+
+- Before: [image](before-l151-1-2-0-upper-landing.jpg)
+- After: [image](after-l156-1-2-0-upper-landing.jpg)
+
+## passage/1-2/0 / lower landing
+
+- Before: [image](before-l151-1-2-0-lower-landing.jpg)
+- After: [image](after-l156-1-2-0-lower-landing.jpg)
+
+## passage/2-3/0 / upper landing
+
+- Before: [image](before-l151-2-3-0-upper-landing.jpg)
+- After: [image](after-l156-2-3-0-upper-landing.jpg)
+
+## passage/2-3/0 / lower landing
+
+- Before: [image](before-l151-2-3-0-lower-landing.jpg)
+- After: [image](after-l156-2-3-0-lower-landing.jpg)
+
+Capture quality failures: 0/12.