Feature mirrors and patterns: preserve replay and add Flip/Center placement (#1619)

Thanks @Karl-VonRichter.

crates/engine/src/cmd/sketch_pattern.rs

@@ -1,8 +1,9 @@
 //! Associative sketch patterns. Editing retains ids at surviving instance indices.
 
-use solidcraft_sketch::{PatternAlignment, PatternInstance, SketchPattern, SketchPatternKind};
+use solidcraft_sketch::{PatternInstance, SketchPattern, SketchPatternKind};
 
 use super::*;
+use crate::cmd::{alignment_param, reversed_param};
 
 pub(super) fn run(s: &mut Session, p: &Value, circular: bool) -> Result<Value> {
     let cmd = if circular { "sketch.pattern.circular" } else { "sketch.pattern.rectangular" };
@@ -257,16 +258,6 @@ fn direction_ref(sk: &Sketch, p: &Value, key: &str, cmd: &str) -> Result<Option<
     }
 }
 
-fn alignment_param(p: &Value, key: &str, cmd: &str) -> Result<PatternAlignment> {
-    p.get(key).map_or(Ok(PatternAlignment::default()), |value| {
-        serde_json::from_value(value.clone()).map_err(|_| bad(cmd, format!("`{key}` must be left, center or right")))
-    })
-}
-
-fn reversed_param(p: &Value, key: &str, cmd: &str) -> Result<bool> {
-    p.get(key).map_or(Ok(false), |value| serde_json::from_value(value.clone()).map_err(|_| bad(cmd, format!("`{key}` must be true or false"))))
-}
-
 fn line_direction(sk: &Sketch, id: Option<&str>) -> Option<Vec2> {
     let Shape::Line { a, b } = sk.shape(sk.curve_index(id?)?)? else { return None };
     (b - a).normalized()