Weak models emit a desktop dashboard's sidebar either as a full-width band on a
vertical root or crammed into a horizontal row with every section — both render
broken (the removed bespoke scaffold used to pre-build the two-column root).
app_shell::reshape_sidebar_to_app_shell detects a sidebar dashboard and rewrites
it to a horizontal [sidebar(260) | content-column(fill)] shell, run in the shared
cleanup::run_cleanup_passes finalize point (covers orchestrator + agentic loop).
A layout==vertical|none guard on fix_horizontal_overflow stops it re-widening the
narrowed sidebar. Detection is hardened (strong sidebar token + structural
dashboard-content gate) against restaurant/landing/top-nav/mobile/multi-screen
false-positives; 14 unit + 1 integration test, verified end-to-end via op-smoke.
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