Ψ-W1-T2 review remediation: solo restore drops on visible-in-target, not parked; N-mode segments read dead when unroutable

Fixes a hidden-parent solo replay that could silence the mix. Also closes the N-mode segment silent no-op, amends the invariant comment, trims view.cpp under 600 lines, hedges two SDK inferences, drops a dead null-check.

src/shell/actions/design_view_actions.cpp

@@ -162,8 +162,10 @@ void persistViewState() {
 }
 
 // The footer segment already reads disabled while the transport runs, but an action can
-// be fired with the panel closed — so the refusal also lands as a status line. Guarded on
-// the transport because applyMode's other refusal is an unregistered mode id.
+// be fired with the panel closed — so the refusal also goes through Help_Set (SDK
+// documents only the signature, not its display surface; inferred to be visible
+// feedback by name, not confirmed). Guarded on the transport because applyMode's
+// other refusal is an unregistered mode id.
 void reportModeSwitchRefused() {
     if (transportBlocksModeSwitch(nullptr) && Help_Set)
         Help_Set("ReaSampler: stop the transport to switch view mode", true);