Edit sketch text content and placement from its outlines (#253)

* Expose interactive editing and placement of sketch text

* Respect document units when editing sketch text

* Route Edit Text through the shared feature dialog

The sketch text editor is now a Kind::Text dialog opened through
Dialog::for_command (frame.rs docking, standard OK/Cancel, Enter/Esc).
Its fields are ordinary dialog fields: they take expressions, parameters
and units, and bare lengths are in the design's units. Untouched fields
keep their exact saved values. The dialog stays open across unrelated
design changes and closes only when its text is gone, the sketch ends,
or another command starts.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RjGw4gA5ZvKrU8MQP6sBgT

---------

Co-authored-by: bherbruck <brennen.herbruck@gmail.com>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

crates/ui-egui/src/context_menu.rs

@@ -642,6 +642,9 @@ fn sketch_entity_items(app: &SolveApp) -> Vec<Item> {
         return v;
     }
     let ents: Vec<String> = curves.iter().chain(points.iter()).cloned().collect();
+    if crate::sketch_text::selected_entity(app).is_some() {
+        v.push(cmd(app, "sketch.edit_text", "Edit Text"));
+    }
     v.push(cmd(app, "sketch.move", "Move/Copy").key("M"));
     if !curves.is_empty() {
         v.push(cmd(app, "sketch.construction", "Normal / Construction").with(json!({ "curves": curves })));