Guide sketch patterns with live previews and editable offsets (#966)

Sketch Mirror, rectangular and circular Pattern, and Offset now show a green live preview that follows the selection and settings; OK commits, Cancel leaves the sketch unchanged. The shared dialogs show the current selection step and source counts, sources can be toggled with Ctrl/Cmd-click, cleared and reselected.

Offsets keep editable driving distance dimensions (One Side, Two Sides, Symmetric) that update the derived curves without moving the source, with undo/redo and save/reopen. Format 19: older files keep their fixed offsets.

New dialog labels in en, zh, ja, de and ko.

Fixes #696. Fixes #517.

docs/book/src/guide/files.md

@@ -73,7 +73,7 @@ is available. Missing or incompatible pictures use the usual thumbnail generatio
 The default `cache: false` omits the portable thumbnail too.
 The repository's `docs/design-container.md` describes limits and encoding details.
 
-Current designs use format 18, including the style of sketch text (bold, italic, alignment, spacing and the curve it follows), face anchors on a piece of a face by its own name, sheet metal rims and bend ends, bend edges for Convert to Sheet Metal, the tear corner relief of sheet metal rules, the names of projected edges, physical materials defined in the design, the font of sketch text, sheet metal corner relief shapes, sketch face anchors on cylinder caps, sketch axis
+Current designs use format 19, including editable associative offset-distance dimensions, the style of sketch text (bold, italic, alignment, spacing and the curve it follows), face anchors on a piece of a face by its own name, sheet metal rims and bend ends, bend edges for Convert to Sheet Metal, the tear corner relief of sheet metal rules, the names of projected edges, physical materials defined in the design, the font of sketch text, sheet metal corner relief shapes, sketch face anchors on cylinder caps, sketch axis
 links, persistent
 names from exact face history, exact planar shell-face anchors, persistent analytic offset boundary roles and
 association profile references, durable sketch face anchors, periodic fit splines and versioned

docs/book/src/guide/sketching.md

@@ -226,3 +226,22 @@ remain valid in an inch design. Angular dimensions keep their angular units. Del
 retain trailing zeros. Component/canvas distance controls and inspection, parts-library
 and flat-pattern measurements follow design units too; parameter expressions and metric
 standard names retain their explicit authored units.
+
+### Reviewing mirror, pattern, and offset results
+
+Mirror, rectangular/circular Pattern, and Offset show the active selection step in their
+shared tool window. Click an input to change it; click a selected object again or Ctrl/Cmd-click
+it to remove it. Each input has its own Clear button. Source inputs show a count, and single
+references identify the chosen mirror line, direction, or centre. Box selection also works
+while the window is open. Sketch modify tools take geometry from the sketch being edited.
+
+Proposed sketch geometry appears **green** before confirmation. Change the inputs or values to
+update the preview, then press **OK**. **Cancel** discards the preview. A circular pattern centre
+can be an existing point or a position clicked in empty sketch space.
+
+Offset distances are editable driving dimensions: double-click a dimension or change its model
+parameter to resize the offset without moving its source curves. The selected side, distance,
+and association survive save/reopen and undo/redo. Symmetric offsets share one driving distance;
+Two Sides has an independent distance for each side. Disconnected selected curves or chains are
+all offset. Breaking an association retains its current geometry and removes that association's
+driver. Older offsets retain their saved fixed distances.

docs/design-container.md

@@ -7,7 +7,7 @@ self-contained input/output format. `io::write_design` keeps its JSON contract;
 `io::write_design_container` is the fallible container writer.
 
 Packages have `container.json` with `{"format":"solidcraft-container/1"}` and
-`document.json` with the versioned parametric document (currently `solidcraft/18`).
+`document.json` with the versioned parametric document (currently `solidcraft/19`).
 The independent versions let document migrations evolve without changing blob encodings.
 Existing serialized document fields are retained automatically, without a second copy
 of the document schema or a deep clone of embedded payloads.