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.

crates/doc/src/format.rs

@@ -130,12 +130,15 @@
 //!   plate or a face of another body at the same height) is mirrored into that face when the
 //!   design is evaluated. Holes whose direction enters their face build as before.
 
+//! - 19: editable associative offset-distance dimensions. Older offsets retain their saved
+//!   fixed distances; migration does not invent dimensions or change geometry.
+
 use serde_json::Value;
 
 use crate::{DocError, Document, Result};
 
 /// The format this build writes.
-pub const FORMAT: u32 = 18;
+pub const FORMAT: u32 = 19;
 
 pub fn format_string(n: u32) -> String {
     format!("solidcraft/{n}")
@@ -152,7 +155,7 @@ pub fn version_of(s: &str) -> Option<u32> {
 
 /// JSON-level upgrades: entry `i` turns format `i + 1` into `i + 2`.
 type JsonStep = fn(&mut Value) -> Result<()>;
-const JSON_STEPS: [JsonStep; 17] = [
+const JSON_STEPS: [JsonStep; 18] = [
     |_| Ok(()),
     v2_to_v3,
     v3_to_v4,
@@ -170,6 +173,7 @@ const JSON_STEPS: [JsonStep; 17] = [
     |_| Ok(()),
     |_| Ok(()),
     |_| Ok(()),
+    |_| Ok(()),
 ];
 
 /// Stored face and edge names were worked out from geometry before format 14; they get the