Throttle new-content enumeration to 500ms, off the 30/s OnTimer tick

src/shell/panel/panel_state.h

@@ -206,6 +206,13 @@ inline constexpr unsigned int kTooltipDelayMs = 500;
 inline constexpr int kTooltipCharPx = 7;
 inline constexpr int kTooltipTextH  = 14;
 
+// New-content detection's enumeration cadence — matches the VST3 side's own
+// kSyncTimerIntervalMs (editor_platform.cpp), this codebase's established interval for a
+// background poll nothing visible depends on. Auto-tag is an invisible metadata update
+// (see detectNewContent), so a 15x cadence cut (30/s -> 2/s) costs latency no one watches
+// for, not correctness.
+inline constexpr unsigned int kDetectIntervalMs = 500;
+
 // Client area top to bottom: top toolbar | split body | bottom toolbar | footer.
 // 26, not 24: Font::RegionTitle's line box (19px em + Segoe UI's leading) is ~25px, and
 // DT_VCENTER clips to the rect.
@@ -345,12 +352,18 @@ struct PanelState {
     bool previewActive = false;
     bool previewInited = false;  // guards double init / deinit
 
-    // Each timer tick diffs the live track+item GUID set against the previous tick to
-    // auto-tag new content. GuidBaseline self-arms on first observe() so pre-existing
-    // content is never mass-tagged. Project-load re-arm is driven by persist's load
-    // signal, not a ReaProject* compare — a recycled address previously mis-tagged tracks.
+    // Each enumerating tick (kDetectIntervalMs-throttled) diffs the live track+item GUID
+    // set against the prior enumeration to auto-tag new content. GuidBaseline self-arms on
+    // first observe() so pre-existing content is never mass-tagged. Project-load re-arm is
+    // driven by persist's load signal, not a ReaProject* compare — a recycled address
+    // previously mis-tagged tracks.
     GuidBaseline contentBaseline;
     bool         reloadPending = false;  // set by bankPanelNotifyProjectLoaded; drained next detect tick
+
+    // Throttles enumerateLiveGuids to kDetectIntervalMs regardless of how often
+    // bankPanelRefresh itself is called (the OnTimer poll, ~30/s, plus a handful of
+    // post-capture/ingest/bake call sites). 0 forces the very first tick through.
+    unsigned int lastDetectTick = 0;
 };
 
 // Defined in panel_window.cpp (the lifecycle owner).