Fixes #4100

In accordance with the discussions, I have made sure to keep the normative definition concise and succinct, and move any exemplification or explanation into note since otherwise would be a denormalization of spec itself, especially for the rules of abstract float accuracy, directly linked in the text.

Per discussion at the Editors' call, I'm creating as draft. All feedback will be deeply appreciated.

TODO:

• Add a representative approximation value in the row, probably as a standalone column (double precision)
• Add code points for non-ASCII identifier names
• Add code example to illustrate why PI_2 is redundant per WGSL definitions