Windows installer: fix the Windows build and register the browser host

- main.rs: the Windows clipboard branch dropped the copy's Result (only the non-Windows branch was
  checked), which failed to compile for Windows; both now report a failed copy.
- windows/hooks.nsh: the NSIS installer writes the native messaging manifests next to kestrove-nmh.exe
  and registers them under HKCU for Chrome, Chromium, Edge, Brave, Vivaldi and Firefox; uninstall
  removes them. Per-user install.
- scripts/windows.sh: cross-build with cargo-xwin, compile the installer with NSIS 3.11 in a Debian 13
  container (Homebrew's makensis 3.13 crashes on macOS).

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src-tauri/tauri.conf.json

@@ -10,14 +10,42 @@
     "frontendDist": "../dist"
   },
   "app": {
-    "windows": [{ "title": "Kestrove", "width": 1040, "height": 680, "minWidth": 760, "minHeight": 480, "titleBarStyle": "Overlay", "hiddenTitle": true }],
+    "windows": [
+      {
+        "title": "Kestrove",
+        "width": 1040,
+        "height": 680,
+        "minWidth": 760,
+        "minHeight": 480,
+        "titleBarStyle": "Overlay",
+        "hiddenTitle": true
+      }
+    ],
     "security": {
       "csp": "default-src 'self'; script-src 'self'; style-src 'self'; img-src 'self' data:; connect-src ipc: http://ipc.localhost"
     }
   },
   "bundle": {
     "active": true,
-    "targets": ["msi", "nsis", "appimage", "deb"],
-    "icon": ["icons/32x32.png", "icons/128x128.png", "icons/[email protected]", "icons/icon.icns", "icons/icon.ico", "icons/icon.png"]
+    "targets": [
+      "msi",
+      "nsis",
+      "appimage",
+      "deb"
+    ],
+    "icon": [
+      "icons/32x32.png",
+      "icons/128x128.png",
+      "icons/[email protected]",
+      "icons/icon.icns",
+      "icons/icon.ico",
+      "icons/icon.png"
+    ],
+    "windows": {
+      "nsis": {
+        "installerHooks": "windows/hooks.nsh",
+        "installMode": "currentUser"
+      }
+    }
   }
 }