Fix stale hover latch on drag release, tooltip anchor, border off-by-one; pin gutter golden test, drop DPI framing

src/shell/instrument/editor_input.cpp

@@ -79,6 +79,11 @@ void ReaSamplerEditor::onMouseUp(int x, int y) {
     drag_ = DragKind::kNone;
     dragParamId_ = -1;
     curvePointIndex_ = -1;
+    // hover_ is deliberately not re-resolved during a drag (see resolveHover's caller), so it
+    // still names wherever the drag started. Re-resolve now against the release position, for
+    // every drag kind — otherwise the next paint latches a stale hover (wrong note name/tooltip,
+    // wrong control outline) until the next WM_MOUSEMOVE.
+    resolveHover(x, y);
     // A scrollbar drag is transient UI (no parameter change), and the processor-side knobs
     // (the preview-velocity -2 sentinel, voice count, master gain) are per-instance settings
     // that don't reload the instrument. Master gain is an atomic the audio thread reads