feat(version): V4 beta-in-isolation channel via -DREASAMPLER_CHANNEL

Compile-time channel flag forks a fully isolated reaper_reasampler_beta
(namespace, command-id prefix, action names, dock ident, -beta render) from
one auditable app_version definition. Stable identity byte-unchanged.

src/render_settings.cpp

@@ -207,14 +207,15 @@ const std::vector<CaptureActionDef>& captureActionTable() {
     // 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.
-        {"CEREBELLUM_REASAMPLER_CAPTURE_ITEM",
-         "ReaSampler: capture selected item(s)", "item",
+        // Item scope — item/take FX only. Suffix + phrase are channel-agnostic; the shell
+        // composes the FOREVER-STABLE id (prefix + "CAPTURE_ITEM") and the display name.
+        {"CAPTURE_ITEM",
+         "capture selected item(s)", "item",
          CaptureScope::Item},
 
         // Track scope — item FX + the track's own FX.
-        {"CEREBELLUM_REASAMPLER_CAPTURE_TRACK",
-         "ReaSampler: capture selected track(s)", "track",
+        {"CAPTURE_TRACK",
+         "capture selected track(s)", "track",
          CaptureScope::Track},
     };
     return table;