How much delay (Tarakh) after completing Tashahhud in the first sitting is permitted before it triggers the necessity of Sujud al-Sahw?

The Necessary Acts of Prayer Part 2: Sittings, Testimony, and Cong.

• Merely taking a breath.
• Delaying long enough to recite the blessings upon the Prophet ﷺ up to "Allahumma salli 'ala Muhammad".
• Exactly five minutes.
• No delay is ever penalized.