feat: preserve adaptive sketch profiles and curved modeling workflows

docs/book/src/guide/sketching.md

@@ -4,6 +4,13 @@ A sketch lies on a plane: an origin plane, a construction plane or a planar face
 **Create Sketch** (`sketch.create`) and click a plane, or pick a face first. **Finish Sketch**
 returns to the model.
 
+Curves adapt to the current zoom and display scale. Picking and highlighting use the same
+visible boundary, including small circles at Fit and sketches in rotated components.
+Profile shading follows those curves while preserving holes. Zooming changes the display
+without changing sketch geometry, dimensions, or undo history.
+On short windows or enlarged displays, the Sketch Palette's options scroll while its
+constraint status and **Finish Sketch** button remain visible.
+
 ## Geometry
 
 Lines and polylines (L), rectangles (two-point R, three-point, centre), circles (centre C,
@@ -24,6 +31,21 @@ Extend finds intersections with exact ellipses, rational conics and spline spans
 original line or circular support and extends only beyond the selected endpoint; conflicting
 constraints or an ambiguous overlap leave the sketch unchanged.
 
+Closed convex chains of tangent lines and circular arcs support inward offsets that consume
+a rounded corner. When the offset passes the corner radius, the neighbouring straight
+supports meet at a sharp corner. The surviving lines and endpoint IDs stay stable; the
+retired arcs return under their original IDs if a later edit restores their radius.
+Whole-boundary profile selections follow this transition through save and reopen, so an
+extruded lip can remain associative. Existing eligible closed analytic offsets upgrade
+without changing their saved geometry or IDs.
+
+This transition requires a closed convex boundary with tangent junctions and a certified
+nonempty region. An extinguished arc referenced individually by a constraint or another
+offset cannot retire. Creating another offset from an already sharp retired boundary also
+requires breaking its association first. Open, nonconvex and mixed free-form chains keep
+their existing behavior. Break Offset Association freezes the current boundary, including
+private arc centres and construction flags, for independent editing.
+
 Offsets of smooth ellipses, conics and splines follow their source after dimension changes,
 dragging and reopening a design. Their stored cubic spline has a whole-span normal-distance
 error bound of 0.002 mm. Singular tangents, curvature cusps, possible self-intersections and