passages: smoothed open-air shell joins (L110, v257) - partial, not merged

Bands = end profiles of per-control-span shell capsules (~9.35 m pitch = span spacing).
Shell now smooth-unions adjacent spans over 6 m and reuses the interior chord distance; a 0.60 m
clearance fades in 5-20 m from each mouth. Close-ups: bands reduced but still visible on part of
the exposed shell. Cost vs L109: near-ready +8..+12% (FI 0.88 -> 1.00, TN 0.92 -> 1.01 s @W12).
Audits, Clang/GCC determinism, fast tier and Linux UE build pass. Kept on its own branch.

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

Standalone/Research/WorldAssemblerM3/Linux110/captures/contact-sheets/INDEX.md

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+# L110 capture contact sheets
+
+- [before openair-view-1](before-openair-view-1.png) — 9 views
+- [before openair-view-2](before-openair-view-2.png) — 9 views
+- [before openair-view-3](before-openair-view-3.png) — 9 views
+- [before openair-closeups](before-openair-closeups.png) — 11 views
+- [before mouths](before-mouths.png) — 6 views
+- [before stations](before-stations.png) — 9 views
+- [after openair-view-1](after-openair-view-1.png) — 9 views
+- [after openair-view-2](after-openair-view-2.png) — 9 views
+- [after openair-view-3](after-openair-view-3.png) — 9 views
+- [after openair-closeups](after-openair-closeups.png) — 11 views
+- [after mouths](after-mouths.png) — 6 views
+- [after stations](after-stations.png) — 9 views