docs: add update manifest schema

Formal JSON schema for the release manifest, with canonical ordering
rules so signatures stay stable. Includes a small synthetic example
under docs/examples/.

docs/examples/manifest-example.json

@@ -0,0 +1,52 @@
+{
+  "version": "2026.04.14-1",
+  "created_at": "2026-04-14T14:00:00Z",
+  "previous": "2026.04.13-3",
+  "notes": "synthetic example showing the manifest structure. a real manifest covers tens of thousands of files.",
+  "launcher": {
+    "path": "Metin2Launcher.exe",
+    "sha256": "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855",
+    "size": 15728640,
+    "platform": "windows"
+  },
+  "files": [
+    {
+      "path": "Metin2.exe",
+      "sha256": "2653e87ecd8ba305b70a96098788478e8b60c125ec83bcd1307486eafb5c5289",
+      "size": 27982848,
+      "platform": "windows"
+    },
+    {
+      "path": "assets/root/serverinfo.py",
+      "sha256": "b564fef7e45326ff8ad1b188c49cd61d46af1b07de657689814526725919d5cb",
+      "size": 9231
+    },
+    {
+      "path": "config.exe",
+      "sha256": "a79c4e0daef43ce3a2666a92774fc6a369718177e456cb209fabe02ca640bcc2",
+      "size": 258048,
+      "platform": "windows"
+    },
+    {
+      "path": "pack/item.pck",
+      "sha256": "7aa9d46724a921fecf5af14c10372d0d03922e92a4cace4b5c15c451416f36b7",
+      "size": 128547328
+    },
+    {
+      "path": "pack/locale.pck",
+      "sha256": "3b9dfe45317a14fcb70a138c1b9d57d984fe130e833c4341deaaff93d615ac67",
+      "size": 4587520
+    },
+    {
+      "path": "pack/metin2_patch_easter1.pck",
+      "sha256": "2dab6a06d317014782cbe417d68dd3365d1d8c7cc35daa465611ce2108547706",
+      "size": 12345600,
+      "required": false
+    },
+    {
+      "path": "pack/uiscript.eix",
+      "sha256": "79bd367b31882e52dfa902f62112f5d43831673ed548ebbd530e2f86dfa77d14",
+      "size": 892416
+    }
+  ]
+}