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/core/ui/footer_bar.h

@@ -65,7 +65,11 @@ FooterHit hitTestFooterBar(int px, int py, const FooterBarLayout& layout);
 // plays or records (shell/view::transportBlocksModeSwitch), so an unreachable segment must READ
 // dead before the click, not merely refuse on it. The ACTIVE segment stays live regardless: it
 // fires a reapply, which is never gated, and dimming the mode you are already in would read as
-// "this mode is unavailable" rather than "you cannot leave it right now".
-bool modeSegmentEnabled(bool isActiveSegment, bool transportRunning);
+// "this mode is unavailable" rather than "you cannot leave it right now". `routable` is whether
+// the shell resolved a live command id for this segment (the model is N-mode, the UI ships two
+// seeded ids — a third registered mode has no action to route through, so its segment must read
+// dead rather than paint live and silently no-op on click). Passed IN so this predicate — and
+// `core/ui` — stays REAPER-free, exactly as `transportRunning` is.
+bool modeSegmentEnabled(bool isActiveSegment, bool transportRunning, bool routable);
 
 } // namespace reasampler::ui