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/view/view.h

@@ -3,7 +3,8 @@
 // ViewModeModel's pure planner, and applies the resulting flag / per-FX /
 // lane writes. The .cpp is the sole REAPER-facing TU here (CLAUDE.md contract:
 // only main.cpp defines the API pointers). See src/shell/view/CLAUDE.md for
-// the enforced invariants (never touch master/mute/solo, snapshot-based restore).
+// the enforced invariants (never touch master/mute, solo cached per mode and
+// never lost, snapshot-based restore).
 
 #include <string>
 
@@ -17,7 +18,9 @@ namespace reasampler {
 // True while `proj`'s transport is playing or recording — the condition under which
 // applyMode refuses a real mode switch. Exposed so the panel can paint the footer's
 // [Arrange|Design] segments disabled BEFORE the click rather than only refusing on
-// it. `proj` == nullptr means the current project.
+// it. `proj` is passed through to GetPlayStateEx as-is; the SDK documents proj=0
+// meaning "current project" for GetTrack but is silent on GetPlayStateEx, so
+// `nullptr` meaning the current project here is inferred by analogy, not confirmed.
 bool transportBlocksModeSwitch(ReaProject* proj);
 
 // Snapshots each about-to-park track's flags into `model`, caches/clears the