tooltip: clamp box width to client on narrow panels; add narrow-client test

src/bank_panel.cpp

@@ -1098,6 +1098,9 @@ bool currentTooltip(int w, int h, std::string& textOut, int& ax, int& ay, int& a
 
     // The full name is stored already prefix-free, but strip defensively in case a source ever
     // carries the "ReaSampler:" display prefix (the tooltip must never show it — L5 refinement 2).
+    // Intentionally distinct sources: the tooltip reads the registered phrase (fullName) while the
+    // keybinding sub-row in drawToolbar reads the live binding via kbd_getTextFromCmd. Do not
+    // unify them — each serves a different purpose and has a different lifetime.
     textOut = stripActionPrefix(rows[static_cast<std::size_t>(hv.index)].fullName,
                                 actionDisplayPrefix());
     ax = slot->x; ay = slot->y; aw = slot->width; ah = slot->height;

src/tooltip.cpp

@@ -18,7 +18,10 @@ TooltipBox computeTooltip(int anchorX, int anchorY, int anchorW, int anchorH,
     TooltipBox box;
     if (textW <= 0 || textH <= 0 || clientW <= 0 || clientH <= 0) return box;
 
-    const int boxW = textW + 2 * spec.padX;
+    // Clamp boxW so it never exceeds the available client span; then clamp x so the (possibly
+    // reduced) box always sits within [margin, clientW - margin].
+    const int maxBoxW = clientW - 2 * spec.margin;
+    const int boxW = (textW + 2 * spec.padX < maxBoxW) ? textW + 2 * spec.padX : maxBoxW;
     const int boxH = textH + 2 * spec.padY;
 
     // Horizontal: centre on the anchor, then clamp within [margin, clientW - margin - boxW].