Fix Cowork model selection and Windows CLI packaging (#1129)

Cherry-picked from upstream PR #1129 + local improvements:
- dedupe inline remove-model handler -> use handleRemoveModel
- add .next-cli-build/ and cli/.build-home/ to .gitignore

postcss.config.mjs

@@ -1,6 +1,12 @@
+import path from "node:path";
+import { fileURLToPath } from "node:url";
+
+const projectRoot = path.dirname(fileURLToPath(import.meta.url));
+
 export default {
   plugins: {
-    "@tailwindcss/postcss": {},
+    "@tailwindcss/postcss": {
+      base: projectRoot,
+    },
   },
 };
-