Fix Insert-as-FX review findings: id rename, selection-count drift, refusal tooltip, success msg, master-only, reserve test

Renames the permanent action id out of the placement family, makes the button's
painted state and pressed outcome share one selection count, surfaces
panel-known refusals in the tooltip, reports the target track on success,
distinguishes a master-only selection, and pins the overflow-reserve test to the
real bar spec.

src/shell/panel/panel_layout.cpp

@@ -131,11 +131,14 @@ std::vector<ActionBarRow> topBarRows() {
     // The one top-bar row with a live/dead gate: it places the PLAYER, and one instance
     // holds one capture. Only the payload half of the fold is knowable at draw time —
     // core/ui/insert_fx_enable.h states why the track half stays a press-time message.
-    rows.push_back({"INSERT_AS_FX", "Insert as FX",
+    // Counts through focusedSelectionIds() (not the raw selection) so the drawn state
+    // can't diverge from doInsertAsFx's own count — the raw selection can go stale
+    // against live membership (e.g. an undo/redo book restore) without being cleared.
+    rows.push_back({"LOAD_INSTRUMENT_ON_TRACK", "Insert as FX",
                     "insert selected sample as ReaSampler 9000 on the selected track",
                     ActionCluster::Placement,
                     insertFxButtonEnabled(
-                        static_cast<int>(g_panel.selection.indices.size()))});
+                        static_cast<int>(focusedSelectionIds().size()))});
     return rows;
 }
 
@@ -276,12 +279,27 @@ bool currentTooltip(int w, int h, std::string& textOut, int& ax, int& ay, int& a
         if (s.index == hv.index) { slot = &s; break; }
     if (!slot) return false;
 
+    const ActionBarRow& row = rows[static_cast<std::size_t>(hv.index)];
+
+    // Insert as FX paints dead only for the payload axis (NoCapture/MultiCapture);
+    // speak that refusal here rather than the generic phrase, so a dead button says
+    // WHY. NoTrack stays a press-time message (insert_fx_enable.h: track selection
+    // has no change callback, so it is only ever knowable at press time).
+    if (row.suffix == "LOAD_INSTRUMENT_ON_TRACK" && !row.enabled) {
+        const InsertFxRefusal refusal =
+            insertFxRefusal(static_cast<int>(focusedSelectionIds().size()), /*trackSelected=*/true);
+        if (refusal != InsertFxRefusal::None) {
+            textOut = insertFxRefusalMessage(refusal);
+            ax = slot->x; ay = slot->y; aw = slot->width; ah = slot->height;
+            return true;
+        }
+    }
+
     // fullName is stored prefix-free; strip defensively in case a source ever
     // carries the display prefix. Tooltip carries name + binding when bound
     // (e.g. "capture selected item — F5"), name only when unbound.
-    const std::string phrase = stripActionPrefix(rows[static_cast<std::size_t>(hv.index)].fullName,
-                                                 actionDisplayPrefix());
-    const int cmd = resolveBarCommandId(rows[static_cast<std::size_t>(hv.index)]);
+    const std::string phrase = stripActionPrefix(row.fullName, actionDisplayPrefix());
+    const int cmd = resolveBarCommandId(row);
     const std::string binding = barBindingText(cmd);
     textOut = binding.empty() ? phrase : phrase + " \xe2\x80\x94 " + binding;  // " — " (em dash, UTF-8)
     ax = slot->x; ay = slot->y; aw = slot->width; ah = slot->height;

src/shell/panel/panel_state.h

@@ -135,6 +135,9 @@ using ui::hitTestPruneButton;
 using ui::hitTestSlot;
 using ui::hitTestTabStrip;
 using ui::insertFxButtonEnabled;
+using ui::insertFxRefusal;
+using ui::insertFxRefusalMessage;
+using ui::InsertFxRefusal;
 using ui::kCardNameScrimAlpha;
 using ui::kCardStripHeight;
 using ui::kCardStripPad;