S17 drop-and-load onto track FX button; S13 editor drop-accept (relay degraded)

S17: drag_out InstrumentDrop gesture + instrument_drop blob reusing the
instrument's own serializer; bank_panel FX hover-track + add-VST/vst_chunk
inject. S13 relay deferred (read-only bridge) — editor shows drop affordance.

src/vst/reasampler_editor.h

@@ -114,6 +114,13 @@ private:
     void onMouseWheel(int delta);           // S12 browser scroll (wheel)
     void onSearchChar(unsigned int ch);     // S12 type-to-filter search keystroke
 
+    // S13 (relay degraded): an OS file drop landed on the editor window. We do NOT ingest (the
+    // instrument is a read-only bank consumer and the relay is unshipped) — we flash the "drop
+    // on the ReaSampler panel to add" affordance so the drop is never silently swallowed and the
+    // shipped ingest gesture stays discoverable. `droppedCount` is how many files were dropped
+    // (drawn into the banner). NEVER inserts a timeline item / never touches the bank.
+    void onFilesDropped(int droppedCount);
+
     // The S9/S8 change-detection tick (WM_TIMER on the child window — the UI thread, NEVER the
     // audio thread). Polls the processor's bank-sync (generation change -> hands-free reload;
     // a new assignment request -> apply as this instance's selection) and, when anything
@@ -212,6 +219,17 @@ private:
     std::string activeFilterBankId_;      // "" = All; else a bank id from banks_
     int selectedZone_ = -1;               // highlighted zone in the Zones panel; -1 = none
 
+    // --- S13 drop-to-load affordance (relay DEGRADED — transient, never persisted) ----
+    // S13's cross-artifact ingest relay (editor drop -> extension ingest) is NOT shipped: the
+    // instrument's REAPER bridge is deliberately READ-ONLY (it never writes the bank / ext
+    // state), so an editor drop cannot relay a bank-ingest request without a new write seam +
+    // an extension-side poller (surfaced as a decision, not crossed here). The DEGRADE path per
+    // the spec: the editor ACCEPTS the drop (WM_DROPFILES) and, rather than silently swallowing
+    // it, flashes a clear affordance pointing at the shipped ingest gesture (drop onto the
+    // docked ReaSampler panel). When > 0, the affordance banner is shown; each sync tick decays
+    // it so it auto-dismisses. No file is ingested, no timeline item is ever inserted.
+    int dropHintTicks_ = 0;               // remaining sync ticks to show the drop affordance
+
     // --- S12 browser scroll + search (transient UI state, never persisted) --------
     int scrollOffset_ = 0;                // vertical px offset into the card grid (clamped)
     std::string searchQuery_;             // type-to-filter narrow; "" = no search