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>

kernels/LevelsPixels.h

@@ -0,0 +1,4 @@
+#include <stdint.h>
+#include <stddef.h>
+void levels_apply(uint8_t *pixels, size_t count, const float *tables);
+void levels_histogram(const uint8_t *pixels, const uint8_t *coverage, size_t count, double *bins);