feat: better diagnostic visuals in status bar

internal/tui/styles/icons.go

@@ -9,3 +9,16 @@ const (
 	HintIcon    string = "ⓗ"
 	SpinnerIcon string = "⟳"
 )
+
+// CircledDigit returns the Unicode circled digit/number for 0‑20.
+// out‑of‑range → "".
+func CircledDigit(n int) string {
+	switch {
+	case n == 0:
+		return "\u24EA" // ⓪
+	case 1 <= n && n <= 20:
+		return string(rune(0x2460 + n - 1)) // ①–⑳
+	default:
+		return ""
+	}
+}