docs: define MSIX-first packaging design and roadmap

Document package formats, release workflows, deployment planning and UI concepts.

Closes #1

docs/code-design/examples/msix.package-project.json

@@ -0,0 +1,59 @@
+{
+  "schemaVersion": 2,
+  "product": {
+    "displayName": "Sample Desktop Tool",
+    "manufacturer": "Example Publisher",
+    "displayVersion": "1.0.0"
+  },
+  "sources": [
+    {
+      "alias": "appPayload"
+    }
+  ],
+  "files": [
+    {
+      "id": "application",
+      "source": "appPayload",
+      "include": [
+        "**/*"
+      ],
+      "exclude": [],
+      "targetRelativePath": "",
+      "required": true
+    }
+  ],
+  "formats": {
+    "msix": {
+      "identity": {
+        "name": "ExamplePublisher.SampleDesktopTool",
+        "publisher": null,
+        "version": "1.0.0.0",
+        "architecture": "x64"
+      },
+      "minimumOsVersion": "10.0.19041.0",
+      "applications": [
+        {
+          "id": "App",
+          "executable": "SampleTool.exe",
+          "entryPoint": "Windows.FullTrustApplication",
+          "square44x44Logo": "Assets/Logo44.png",
+          "square150x150Logo": "Assets/Logo150.png"
+        }
+      ],
+      "capabilities": [
+        "runFullTrust"
+      ],
+      "extensions": [],
+      "dependencies": []
+    }
+  },
+  "targets": [
+    {
+      "id": "msix-direct",
+      "format": "msix",
+      "delivery": "package",
+      "distribution": "direct",
+      "signingProfileRef": null
+    }
+  ]
+}