Checkpoint 5: complete asset freshness, schema migrations and editor diagnostics

include/faset/editor/debug_overlay.hpp

@@ -0,0 +1,24 @@
+#pragma once
+#include <faset/render/renderer.hpp>
+#include <memory>
+#include <span>
+
+namespace faset::editor {
+// Optional developer diagnostics. This module never edits authoring or runtime state.
+class DebugOverlay {
+  public:
+    DebugOverlay();
+    ~DebugOverlay();
+    DebugOverlay(const DebugOverlay&) = delete;
+    DebugOverlay& operator=(const DebugOverlay&) = delete;
+    bool visible() const;
+    void set_visible(bool);
+    // F12 toggles the overlay; events captured by its widgets are removed for this frame.
+    std::vector<render::Event> process_events(std::span<const render::Event>);
+    void append(render::Snapshot&, const render::Renderer&, float delta_seconds);
+
+  private:
+    struct Impl;
+    std::unique_ptr<Impl> impl_;
+};
+} // namespace faset::editor