Call patch invoke on control + c (#15)

<!-- mesa-description-start -->
## TL;DR

Handles `Control+C` during an `invoke` command to gracefully terminate
the remote session by updating its status to `failed`.

## Why we made these changes

Previously, interrupting an `invoke` command with `Control+C` would only
terminate the local CLI process, leaving the remote session running.
This could lead to orphaned resources and unexpected behavior. This
change ensures that when a user cancels an operation, the remote session
is properly cleaned up.

## What changed?

- **`cmd/invoke.go`**:
    - Implemented a signal handler to catch `SIGINT` (`Control+C`).
- On cancellation, the CLI now sends a patch request to mark the remote
invocation as 'failed' with a user-cancelled message.
- Reordered the invocation creation process to ensure the `invocationID`
is available immediately for the cancellation handler.

<sup>_Description generated by Mesa. [Update
settings](https://app.mesa.dev/onkernel/settings/pull-requests)_</sup>
<!-- mesa-description-end -->

Author: hiroTamada

cmd/invoke.go

@@ -92,16 +92,23 @@ func runInvoke(cmd *cobra.Command, args []string) error {
 		return nil
 	}
 
-	// this is a little indirect but we try to fail out of the invocation by deleting the
-	// underlying browser sessions
+	// On cancel, mark the invocation as failed via the update endpoint
 	once := sync.Once{}
 	onCancel(cmd.Context(), func() {
 		once.Do(func() {
 			cleanupStarted.Store(true)
 			defer close(cleanupDone)
 			pterm.Warning.Println("Invocation cancelled...cleaning up...")
-			if err := client.Invocations.DeleteBrowsers(context.Background(), resp.ID, option.WithRequestTimeout(30*time.Second)); err != nil {
-				pterm.Error.Printf("Failed to cancel invocation: %v\n", err)
+			if _, err := client.Invocations.Update(
+				context.Background(),
+				resp.ID,
+				kernel.InvocationUpdateParams{
+					Status: kernel.InvocationUpdateParamsStatusFailed,
+					Output: kernel.Opt(`{"error":"Invocation cancelled by user"}`),
+				},
+				option.WithRequestTimeout(30*time.Second),
+			); err != nil {
+				pterm.Error.Printf("Failed to mark invocation as failed: %v\n", err)
 			}
 		})
 	})