Collapse RunWithOpts duplicates into variadic options

Run, RunStreamed, and Resume each shipped both a no-options form and a
mirror *WithOpts form taking variadic RunOption. Variadic parameters
are backward-compatible additions, so the wrappers were dead surface.

Make Run, RunStreamed, and Resume directly variadic and update the two
internal callers.

Signed-off-by: Aurélien Sibiril <81782+aureliensibiril@users.noreply.github.com>

pkg/agent/restore_test.go

@@ -480,7 +480,7 @@ func TestRestore(t *testing.T) {
 			close(stopCh)
 			ctx := agent.WithStopSignal(context.Background(), stopCh)
 
-			_, err := ag.RunWithOpts(
+			_, err := ag.Run(
 				ctx,
 				[]llm.Message{
 					{