Fix Screen Recording hint and skip usage reads for missing CLIs

internal/agents/codex.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"log/slog"
 	"os"
+	"os/exec"
 	"strings"
 	"time"
 
@@ -275,7 +276,11 @@ func imageBlock(mime, data string) map[string]any {
 }
 
 func (m *Manager) readCodexRateLimit() {
-	err := os.MkdirAll(m.codexHome, 0o700)
+	_, err := exec.LookPath("codex")
+	if err != nil {
+		return
+	}
+	err = os.MkdirAll(m.codexHome, 0o700)
 	if err != nil {
 		slog.Error("read codex rate limits", "err", err)
 		return