Build offline OpenPrestige release bundles

Rename the injector and package it with an embedded payload for Windows, Linux, and macOS x64/ARM64. Add a core-only ImGui native build, multi-platform CI and release packaging, and shared per-user storage with legacy config migration.

scripts/imgui-core/SmokeTest.java

@@ -0,0 +1,59 @@
+import imgui.ImDrawList;
+import imgui.ImFontConfig;
+import imgui.ImGui;
+import imgui.ImGuiIO;
+import imgui.type.ImInt;
+import imgui.type.ImString;
+import java.nio.ByteBuffer;
+import java.nio.file.Files;
+import java.nio.file.Path;
+
+/** Exercises core JNI entry points, real UI fonts, input widgets and draw data without a game. */
+public final class SmokeTest {
+    public static void main(String[] args) throws Exception {
+        ImGui.createContext();
+        try {
+            ImGuiIO io = ImGui.getIO();
+            io.setIniFilename(null);
+            io.setDisplaySize(1000, 600);
+            io.setDeltaTime(1.0f / 60);
+            ImFontConfig config = new ImFontConfig();
+            try {
+                config.setPixelSnapH(true);
+                io.getFonts().addFontFromMemoryTTF(Files.readAllBytes(Path.of(args[0])), 18, config);
+            } finally {
+                config.destroy();
+            }
+            if (!io.getFonts().build()) throw new AssertionError("Font atlas did not build");
+            ImInt width = new ImInt();
+            ImInt height = new ImInt();
+            ByteBuffer pixels = io.getFonts().getTexDataAsRGBA32(width, height);
+            if (pixels == null || width.get() <= 0 || height.get() <= 0) {
+                throw new AssertionError("Font atlas is empty");
+            }
+            ImString input = new ImString("OpenPrestige", 64);
+            float[] value = {0.5f};
+            int vertices = 0;
+            for (int frame = 0; frame < 3; frame++) {
+                ImGui.newFrame();
+                ImGui.setNextWindowSize(500, 350);
+                ImGui.begin("Core JNI smoke test");
+                ImGui.text("OpenPrestige core-only ImGui");
+                ImGui.button("Inject");
+                ImGui.sliderFloat("Scale", value, 0, 1);
+                ImGui.inputText("Config name", input);
+                ImDrawList draw = ImGui.getWindowDrawList();
+                draw.addCircleFilled(100, 100, 20, 0xff80a0ff);
+                draw.addText(120, 100, 0xffffffff, "Draw list");
+                ImGui.end();
+                ImGui.render();
+                vertices = ImGui.getDrawData().getTotalVtxCount();
+            }
+            if (vertices <= 0) throw new AssertionError("No UI geometry was generated");
+            System.out.println("Core JNI passed. Font atlas " + width.get() + "x" + height.get()
+                    + ", vertices " + vertices);
+        } finally {
+            ImGui.destroyContext();
+        }
+    }
+}