Describe AI Denoise in the manual as it now is

On for every raw, at the top of the Adjust panel, kept once computed,
and eased off with Strength rather than Keep grain. The timing line is
left as it was; the new model's measured figure replaces it when that
branch lands. The animation still shows the Keep grain slider and
wants recording again.

docs/manual/README.md

@@ -207,18 +207,20 @@ the sensor recorded.
 
 ### AI denoise
 
-For a photograph taken in poor light at a high ISO. `AI Denoise`, in the
-Detail group, replaces how the camera's raw data is turned into colour: a
-network trained on this library's own photographs removes the noise and
-the blotches of colour that come with it, while keeping the fine detail.
-Look at it at 1:1, where noise lives.
+How every raw is developed. `AI Denoise`, at the top of the Adjust panel,
+replaces how the camera's raw data is turned into colour: a network trained
+on this library's own photographs removes the noise and the blotches of
+colour that come with it, while keeping the fine detail. It is on for every
+raw unless you switch it off with `Apply`. Look at it at 1:1, where noise
+lives.
 
-Switch it on with `Apply`. The photograph keeps showing as it was while
-the network works, with its progress in the bar at the top, and changes
-when it is done — a few seconds on a computer with a graphics card, about
-fifteen on its processor alone, longer on the tablet. `Keep grain` puts
-back some of what was removed, as grain without colour, for a picture that
-does not look too smooth.
+The photograph shows the camera's ordinary conversion while the network
+works, with its progress in the bar at the top, and changes when it is
+done — a few seconds on a computer with a graphics card, about
+fifteen on its processor alone, longer on the tablet. The result is kept,
+so a photograph opened again, or exported, does not wait a second time.
+`Strength` eases it off: below 100 % it puts back some of what was removed,
+as grain without colour, for a picture that does not look too smooth.
 
 ![An ISO 8000 night frame at 1:1, AI Denoise switched on, then some grain kept](media/develop-denoise.gif)