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/bank_panel.cpp

@@ -148,6 +148,9 @@ constexpr int kFooterHeight = 26;
 const LICE_pixel kColFooterBg     = LICE_RGBA(20, 20, 22, 255);
 const LICE_pixel kColFooterBorder = LICE_RGBA(70, 70, 76, 255);
 const COLORREF   kRgbFooterText   = RGB(190, 205, 198);
+// Dimmer than the tail label — the version/channel readout is passive identification,
+// not an interactive control, so it recedes visually (V3 unobtrusive placement).
+const COLORREF   kRgbFooterVersion = RGB(120, 128, 124);
 
 // --- Vertical split + region headers + tab strip (Phase B4) -------------------
 //
@@ -528,13 +531,27 @@ void drawTailFooter(LICE_IBitmap* bmp, int w, int h) {
 
     HDC dc = bmp->getDC();
     if (!dc) return;
+    SetBkMode(dc, TRANSPARENT);
+
+    // Tail-mode toggle, left-aligned (the interactive control — footer clicks cycle it).
     const std::string label = tailToggleLabel(currentTail());
     RECT rc = f;
     rc.left += 8;
     SetTextColor(dc, kRgbFooterText);
-    SetBkMode(dc, TRANSPARENT);
     DrawText(dc, label.c_str(), -1, &rc,
              DT_LEFT | DT_VCENTER | DT_SINGLELINE | DT_END_ELLIPSIS);
+
+    // Version/channel readout (Phase V, V3/V4), right-aligned in the same footer strip so
+    // it is always visible but unobtrusive. appVersion() renders "0.9.01" on stable and
+    // "0.9.01-beta" on beta, so a beta panel self-identifies its channel here. Right inset
+    // matches the left inset; DT_RIGHT keeps it clear of the left-aligned tail label
+    // (the two never overlap at normal panel widths — the label is short, the readout is
+    // ~10 chars, and DT_END_ELLIPSIS on both degrades gracefully if a panel is ever tiny).
+    RECT vrc = f;
+    vrc.right -= 8;
+    SetTextColor(dc, kRgbFooterVersion);
+    DrawText(dc, reasampler::appVersion().c_str(), -1, &vrc,
+             DT_RIGHT | DT_VCENTER | DT_SINGLELINE | DT_END_ELLIPSIS);
 }
 
 // True iff client-relative (x, y) falls inside the (non-degenerate) footer strip.
@@ -1993,7 +2010,11 @@ void openPanel() {
                                      GetMainHwnd(), dlgProc, 0);
     if (!g_panel.hwnd) return;
 
-    DockWindowAddEx(g_panel.hwnd, "ReaSampler Bank", "reasampler_bank_panel", true);
+    // Channel-qualified dock identity (Phase V, V4). The title and the persisted-position
+    // identstr both come from app_version, so a beta panel is distinguishable ("ReaSampler
+    // Bank beta") and does not fight over stable's saved dock slot (the identstr is a
+    // REAPER-global collision surface — it keys the persisted dock position).
+    DockWindowAddEx(g_panel.hwnd, dockTitle().c_str(), dockIdent().c_str(), true);
     DockWindowActivate(g_panel.hwnd);
     g_panel.open = true;