feat: strengthen sketches, feature editing, and independent assemblies

docs/book/src/guide/assemblies.md

@@ -11,6 +11,13 @@ component, and **Paste New** creates an independent copy. Move an occurrence wit
 triad, then **Capture Position** to keep it or **Revert** to put it back. SolveCraft asks before
 the next command if a move wasn't captured. **Ground** fixes an occurrence in place.
 
+Paste New copies nested component definitions, sketches, feature histories and generated
+dimension parameters. Repeated child instances remain shared within the new copy. Materials,
+appearances and wholly internal joints/motion records receive copied references. Design-wide
+user parameters remain shared; retained external links and omitted cross-boundary motion
+records are reported. Unsupported destructive links refuse the entire copy. See
+[individual-instance and copy details](https://github.com/bherbruck/solvecraft/blob/main/docs/occurrence-workflows.md).
+
 **Joints** (`joint.create`, J) connect two components by joint origins that snap to faces, edges,
 circles and vertices: rigid, revolute, slider, cylindrical, pin-slot, planar and ball, with
 offsets, flip and limits. **As-built Joint** keeps the current position, **Rigid Group** locks

docs/book/src/guide/features.md

@@ -18,6 +18,22 @@ Extruding into existing material selects **Cut**. In an empty component it selec
 choose **New Body** explicitly to keep an addition separate. Changing the default does not alter
 operations already saved in a design.
 
+Editing an extrusion retains its signed distances, From/To Object inputs, taper expressions
+and explicit body targets. Revolve edits retain world, sketch and explicit-line axes, both
+angle expressions and To Object targets. An unchanged **All profiles** selection continues
+to include profiles added later. Cancel restores the complete timeline; a successful edit is
+one undo step, including downstream parameter changes. Editing a placed component previews the
+edited feature before its downstream history. Cylindrical Emboss profile guides follow the
+sketch's chosen occurrence frame.
+
+For cylindrical **Emboss**, select a supported exterior cylinder face and a tangent sketch
+profile. **Deboss** cuts radially into the wall. Orthogonal line profiles, including holes and
+concave outlines, wrap with exact radial walls; the profile must stay clear of seams and ends.
+Complete cylinders and coaxial sleeves are supported. Capture pending component positions
+before applying. The feature stores the selected target and author occurrence paths, so edits
+and reopening retain the chosen instances. Other curved surfaces and free-form profiles remain
+unsupported; omitting the face retains the planar emboss behavior.
+
 Fillets and chamfers handle straight edges between planar faces, whole smooth loops, runs of
 neighbouring edges with mitred or spherical corners, and closed chains of curved edges (a rolling
 ball). See the roadmap's known limitations for the rest.

docs/book/src/guide/files.md

@@ -17,3 +17,8 @@ Saves are atomic: a crash at any moment leaves either the old file or the new on
 replaced version is kept as `<file>.bak`. Unsaved changes are autosaved to a recovery folder,
 and the next launch offers to recover them. Older design files are upgraded on open, and files
 from a newer version are refused with a message.
+
+Current designs use format 9 for semantic configuration styles, associative free-form offsets
+and explicit cylindrical emboss selections. Older geometry and expressions retain their
+meaning during upgrade; missing new fields use defaults. Association records and occurrence
+paths are bounded and checked before they can alter geometry.

docs/book/src/guide/sketching.md

@@ -15,6 +15,20 @@ fillet, chamfer, offset (O), mirror, patterns, move/copy and scale.
 **Project** (P) and **Intersect** bring model edges into the sketch as linked geometry that
 follows later changes. Sketching on a face projects its edges automatically.
 
+Extend finds intersections with exact ellipses, rational conics and spline spans. It keeps the
+original line or circular support and extends only beyond the selected endpoint; conflicting
+constraints or an ambiguous overlap leave the sketch unchanged.
+
+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
+excessive subdivisions are refused. Offset these curves individually: mixed chain junctions
+currently require separate geometry. `sketch.offset.break` releases an offset for independent
+editing, and undo restores its association. Older independently sampled offsets remain independent.
+Smooth open offsets can be offset again, including bounded refinement after a source edit.
+A closed offset uses a natural cubic spline whose seam can have different end tangents;
+offsetting that result again is refused when the seam has no unique normal.
+
 ## Constraints and dimensions
 
 The solver is SolveCraft's own (damped Gauss–Newton with degree-of-freedom analysis). Constraints: