macOS: check the resource the URL refers to (#12731)

- Fixes https://github.com/ghostty-org/ghostty/issues/12727.
[`NSURL.hasDirectoryPath` doesn't do
this](https://developer.apple.com/documentation/foundation/nsurl/hasdirectorypath).

<img width="977" height="177" alt="image"
src="https://github.com/user-attachments/assets/94f77277-8ef0-4573-8ae1-0e54f810463f"
/>

> We don't need to check this in NewTerminalIntent since AppIntent
already appends `/` to the directory.

- Set error when there is no directory to open with

macos/Sources/Features/Services/ServiceProvider.swift

@@ -42,10 +42,21 @@ class ServiceProvider: NSObject {
         // to their directories because that's the only thing we can open.
         let directoryURLs = Set(
             pathURLs.map { url -> URL in
-                url.hasDirectoryPath ? url : url.deletingLastPathComponent()
+                /// We check file system resources here because
+                /// NSURL doesn't append `/` when reading string contents from pasteboard
+                ///     ```
+                ///     NSURL(pasteboardPropertyList: "/System/Library".propertyList(), ofType: .fileURL)?.hasDirectoryPath
+                ///     ```
+                let isDirectory = (try? url.resourceValues(forKeys: [.isDirectoryKey]))?.isDirectory ?? url.hasDirectoryPath
+                return isDirectory ? url : url.deletingLastPathComponent()
             }
         )
 
+        guard !directoryURLs.isEmpty else {
+            error.pointee = Self.errorNoString
+            return
+        }
+
         for url in directoryURLs {
             var config = Ghostty.SurfaceConfiguration()
             config.workingDirectory = url.path(percentEncoded: false)