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/app/main.cpp

@@ -130,7 +130,10 @@ static std::vector<reasampler::ActionTableRow> buildMainActionTable() {
     rows.push_back({"INSERT_SELECTED_CONFORM",
                     "insert selected sample at edit cursor (conform to tempo)",
                     &RunInsertSelected, 1});
-    rows.push_back({"INSERT_AS_FX",
+    // A LOAD_*, not an INSERT_*: INSERT_SELECTED/_CONFORM place a timeline item;
+    // this loads an instrument onto a track's FX chain. The id is permanent, so
+    // keeping the two apart here is the most durable statement of which verb this is.
+    rows.push_back({"LOAD_INSTRUMENT_ON_TRACK",
                     "insert selected sample as ReaSampler 9000 on the selected track",
                     &RunInsertAsFx});
     // One action fires N captures (per selected item / per razor area); the original