fix: apply point constraints to sketch preselection

docs/book/src/guide/sketching.md

@@ -94,7 +94,12 @@ aligned, horizontal, vertical, radius, diameter and angle dimensions. Each is a
 For Parallel, Perpendicular, Equal, Tangent, Concentric and Collinear, select exactly two
 sketch curves (Shift-click to add the second) and choose the constraint to apply it immediately.
 You can also start the constraint first and then pick its curves. An incomplete or mixed
-selection starts that pick workflow; a rejected constraint keeps the selection for correction.
+selection leaves the tool ready for ordinary picking.
+
+Coincident accepts an exact selection of two points or a point and a curve. Midpoint
+accepts one point and one line, in either selection order. Symmetry accepts two distinct
+points and one symmetry line, regardless of where the line occurs in the selection.
+Successful constraints clear the selection; rejected constraints preserve it.
 
 Under-constrained geometry is blue and fully constrained geometry turns dark, and the status
 shows the remaining degrees of freedom. A constraint or dimension that would over-constrain the