scaffold Flutter Windows desktop target

Add the generated Windows runner tree and register the windows
platform in .metadata. The Flutter SDK revision bump that came with
`flutter create` for windows also re-resolved the transitive pins in
pubspec.lock. .gitignore now excludes the built clide-cli binary on
Windows, matching the existing linux/macos entries.

Co-Authored-By: Claude <noreply@anthropic.com>

.metadata

@@ -4,7 +4,7 @@
 # This file should be version controlled and should not be manually edited.
 
 version:
-  revision: "cc0734ac716fbb8b90f3f9db8020958b1553afa7"
+  revision: "c9a6c484230f8b5e408ec57be1ef71dee1e77020"
   channel: "stable"
 
 project_type: app
@@ -13,11 +13,11 @@ project_type: app
 migration:
   platforms:
     - platform: root
-      create_revision: cc0734ac716fbb8b90f3f9db8020958b1553afa7
-      base_revision: cc0734ac716fbb8b90f3f9db8020958b1553afa7
-    - platform: web
-      create_revision: cc0734ac716fbb8b90f3f9db8020958b1553afa7
-      base_revision: cc0734ac716fbb8b90f3f9db8020958b1553afa7
+      create_revision: c9a6c484230f8b5e408ec57be1ef71dee1e77020
+      base_revision: c9a6c484230f8b5e408ec57be1ef71dee1e77020
+    - platform: windows
+      create_revision: c9a6c484230f8b5e408ec57be1ef71dee1e77020
+      base_revision: c9a6c484230f8b5e408ec57be1ef71dee1e77020
 
   # User provided section