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

src/shell/panel/panel_state.h

@@ -47,6 +47,7 @@
 #include "core/ui/tab_strip.h"
 #include "core/ui/theme.h"
 #include "core/ui/tooltip.h"
+#include "core/util/elapsed_at_least.h"
 #include "core/version/app_version.h"
 #include "core/view/guid_diff.h"
 #include "core/view/lane_keys.h"
@@ -182,6 +183,9 @@ using version::channelCommandId;
 using version::dockIdent;
 using version::dockTitle;
 
+// core/util
+using util::elapsedAtLeast;
+
 // core/wire
 using wire::buildInstrumentDropPreset;
 
@@ -208,9 +212,8 @@ 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.
+// background poll nothing visible depends on. The throttle's correctness argument lives at
+// detectNewContent's own comment (panel_input.cpp) — the authoritative home; not restated here.
 inline constexpr unsigned int kDetectIntervalMs = 500;
 
 // Client area top to bottom: top toolbar | split body | bottom toolbar | footer.
@@ -362,7 +365,10 @@ struct PanelState {
 
     // 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.
+    // post-capture/ingest/bake call sites); the gate's correctness argument lives at
+    // detectNewContent (panel_input.cpp), not restated here. 0 forces the very first tick
+    // through PROVIDED system uptime is already >= kDetectIntervalMs at that call — always
+    // true in practice, but an assumption elapsedAtLeast takes, not one it guarantees.
     unsigned int lastDetectTick = 0;
 };