OmaPhoto 1.0.0: the Linux port of Compositor

A layered image editor for Linux and Omarchy, ported from Compositor
(github.com/robbietilton/Compositor), whose Swift source is its
specification. It reads and writes Compositor's .comp projects.

Packages for Ubuntu, Fedora and Arch come from the release workflow;
scripts/install/ holds one install script per distribution family,
and flake.nix serves NixOS.

Co-Authored-By: Claude <noreply@anthropic.com>

src/Document/SelectionEdits+Session.h

@@ -0,0 +1,23 @@
+// Swift's SelectionEdits extension: fills, clears, moves and inverts.
+public:
+    // The outline the canvas draws.
+    std::optional<DocumentSelection> displayedSelection() const;
+    enum class FillSource { foreground, background };
+    bool canEditPixels() const;
+    void fillSelection(FillSource source, std::function<void()> done = {});
+    void clearSelectedPixels(std::function<void()> done = {});
+    void deleteKeyPressed();
+    // Swift's PixelMove: Ctrl-drag and Ctrl-arrow move selected pixels.
+    bool beginPixelMove(bool duplicate = false);
+    void movePixels(QSizeF offset);
+    void finishPixelMove(std::function<void()> done = {});
+    void cancelPixelMove();
+    void nudgePixels(double dx, double dy, std::function<void()> done = {});
+    void deleteLayerOrMask();
+    bool canInvert() const;
+    // Off the UI thread; `done` follows the step or refusal.
+    void invertPixels(std::function<void()> done = {});
+
+private:
+    void finishInvert();
+    void applyPixelEdit(const ImageLayer &layer, const QString &name, const std::function<void(BrushStroke &)> &paint, std::function<void()> done);