Extract elapsedAtLeast to core/util, dedupe the throttle rationale, and correct the alloc-count/PLAN citations

src/shell/panel/panel_input.cpp

@@ -136,8 +136,8 @@ void enumerateLiveGuids(ReaProject* proj, std::set<std::string>& allGuids,
 
 // One detection tick: REAPER exposes no "item/track added" callback, so this diffs live
 // GUIDs against the baseline and auto-tags the new ones into the active mode. Called every
-// timer tick regardless of panel open/close, but the enumeration itself is throttled to
-// kDetectIntervalMs (see the gate below). READ-ONLY on the project; mutates only the
+// timer tick regardless of panel open/close; the enumeration's throttle and its correctness
+// argument are the gate immediately below. READ-ONLY on the project; mutates only the
 // in-memory membership index — deliberately OUTSIDE any Undo block (auto-tag is a
 // background metadata update, not a destructive edit; an Undo block here would flood
 // REAPER's history with an entry per tick that sees new content).
@@ -147,12 +147,18 @@ void enumerateLiveGuids(ReaProject* proj, std::set<std::string>& allGuids,
 bool detectNewContent() {
     if (!g_panel.session) return false;
 
-    // Throttles the enumeration (O(T+I) REAPER calls + allocations) to kDetectIntervalMs,
-    // independent of how often the caller ticks. A skipped tick leaves reloadPending/the
-    // baseline untouched, so the guards below still run before the NEXT diff whenever this
-    // gate next opens — only the diff's cadence changes, not its correctness.
+    // Throttles the enumeration (O(T+I) REAPER calls + allocations) to kDetectIntervalMs via
+    // elapsedAtLeast (core/util; wraparound-safe against GetTickCount()'s rollover, see its
+    // header). A skipped tick leaves reloadPending/the baseline untouched, so the guards below
+    // still run before the NEXT diff whenever this gate next opens — only the diff's cadence
+    // changes, not its correctness.
+    //
+    // KNOWN CONSEQUENCE, not new: a new item's mode resolves from
+    // preExistingTrackModes()/activeModeId() at ENUMERATION time (below), not creation time, so
+    // switching mode or moving the item before the next tick can land it in a different mode
+    // than a tighter cadence would — the window existed at ~33 ms; now widened ~16x.
     const unsigned int now = GetTickCount();
-    if (now - g_panel.lastDetectTick < kDetectIntervalMs) return false;
+    if (!elapsedAtLeast(now, g_panel.lastDetectTick, kDetectIntervalMs)) return false;
     g_panel.lastDetectTick = now;
 
     ReaProject* proj = EnumProjects(-1, nullptr, 0);
@@ -556,10 +562,10 @@ void bankPanelNotifyProjectLoaded() {
 }
 
 void bankPanelRefresh() {
-    // New-content auto-tag detection is CALLED every tick regardless of panel open/close
-    // (tracks/items are created in the arrange view, not the panel), but the enumeration
-    // it drives is throttled — see kDetectIntervalMs. READ-ONLY on the project; only
-    // mutates the in-memory membership index.
+    // New-content auto-tag detection runs every tick regardless of panel open/close (tracks/
+    // items are created in the arrange view, not the panel); detectNewContent (panel_input.cpp,
+    // above) is the authoritative comment for its throttle, correctness argument, and
+    // read-only/mutation contract.
     const bool tagged = panel::detectNewContent();
 
     // Lane minting runs ONLY when detection just tagged new content — a track can only