refactor(capture): drop master scope; realtime taps selected track

Capture is now item + track only (master removed as a scope; still bypassed
as out-of-scope chain). Realtime records the selected track's own output via
per-track post-fader sends into a hidden temp track, fixing the silent file.

src/render_settings.cpp

@@ -55,9 +55,8 @@ SourceMode sourceModeForScope(CaptureScope scope) {
     switch (scope) {
         case CaptureScope::Item:   return SourceMode::SelectedItems;
         case CaptureScope::Track:  return SourceMode::SelectedTracks;
-        case CaptureScope::Master: return SourceMode::MasterMix;
     }
-    return SourceMode::MasterMix;  // unreachable for a valid enum; fail to master
+    return SourceMode::SelectedItems;  // unreachable for a valid enum; fail closed
 }
 
 RangeSource inferRangeSource(bool hasRazorArea) {
@@ -84,12 +83,6 @@ FxBypassPlan fxBypassPlanFor(CaptureScope scope) {
             p.bypassAncestorFx = true;
             p.bypassMaster     = true;
             return p;
-        case CaptureScope::Master:
-            // Master = whole chain. Bypass nothing.
-            p.bypassSelfFx     = false;
-            p.bypassAncestorFx = false;
-            p.bypassMaster     = false;
-            return p;
     }
     return p;  // unreachable; bypass nothing (fail to full-chain, never over-bypass)
 }
@@ -137,12 +130,13 @@ RazorRange razorUnionBounds(const std::vector<RazorRange>& ranges) {
 }
 
 const std::vector<CaptureActionDef>& captureActionTable() {
-    // Built once (function-local static): three SCOPE actions. Tail OFF for all
+    // Built once (function-local static): two SCOPE actions. Tail OFF for all
     // (exact bounds). Ids are FOREVER-STABLE — never edit a shipped string. Each
     // action infers its range (razor-else-time) at fire time and enforces its
     // FX-scope invariant via fxBypassPlanFor. The M7 CAPTURE_TRACKS_WET /
     // CAPTURE_ITEMS_WET / CAPTURE_RAZOR_WET ids are RETIRED (mirror-unregistered in
-    // main.cpp); CAPTURE_MASTER keeps its shipped id string.
+    // main.cpp); the CAPTURE_MASTER scope action is REMOVED (its id is likewise
+    // mirror-unregistered) — to capture the master you render a track.
     static const std::vector<CaptureActionDef> table = {
         // Item scope — item/take FX only. NEW forever-stable id.
         {"CEREBELLUM_REASAMPLER_CAPTURE_ITEM",
@@ -153,11 +147,6 @@ const std::vector<CaptureActionDef>& captureActionTable() {
         {"CEREBELLUM_REASAMPLER_CAPTURE_TRACK",
          "ReaSampler: capture selected track(s)", "track",
          CaptureScope::Track},
-
-        // Master scope — whole chain. Id string unchanged from M7 (already shipped).
-        {"CEREBELLUM_REASAMPLER_CAPTURE_MASTER",
-         "ReaSampler: capture master", "master",
-         CaptureScope::Master},
     };
     return table;
 }