Fix #392: Cmd+A selects a focused field's text or the type being edited

Select All (Cmd/Ctrl+A) now follows the keyboard, as in Illustrator:

- macOS menu bar: the system menu takes Cmd+A/X/C/V before the window
  sees them, so a focused panel, dialog or search field got the document
  command. `menus::invoke_from_system_menu` (used by `NativeMenu::poll`)
  hands Select All, Cut, Copy and Paste to a focused text field as the
  events its keys would send; clicks on those menu items follow the same
  rule. Other commands, and these with no field focused, run as before.
- Type tool: `select.all` itself selects all of the text being edited
  while the Type tool edits (returns {editing, start, end}), so the menu,
  the shortcut, the control channel and headless MCP (`press_key`) agree.
  The UI's own Select All interception and the Type tool's hard-wired
  Cmd+A are gone; Cmd+A reaches it through the Select All shortcut.
- Windows, Linux and the web already left Cmd+A to a focused field; now
  covered by headless app-frame tests (field, Type tool, canvas).

Docs: docs/mcp.md (Select All while editing type), ROADMAP. Not yet:
Select All across threaded frames (one frame's text is selected).

Co-Authored-By: Claude Opus 5.5 <[email protected]>

apps/vectorcraft/src/main.rs

@@ -61,7 +61,7 @@ impl eframe::App for App {
                 self.menu = Some(native_menu::NativeMenu::install(&mut self.app));
             }
             if let Some(m) = &mut self.menu {
-                m.poll(&mut self.app);
+                m.poll(&mut self.app, ctx);
             }
             open_files(&mut self.app, open_documents::take());
         }

apps/vectorcraft/src/native_menu.rs

@@ -33,7 +33,7 @@ pub struct NativeMenu {
 }
 
 /// Accelerator for a shortcut like "Cmd+Shift+]" (modifier-less shortcuts stay in the app so they
-/// don't steal keys from text fields).
+/// don't steal keys from text fields; a focused field still gets Cmd+A/X/C/V, see [`NativeMenu::poll`]).
 fn accel(sc: &str) -> Option<Accelerator> {
     if !(sc.contains("Cmd") || sc.contains("Ctrl") || sc.contains("Alt") || sc.starts_with('F')) {
         return None;
@@ -72,12 +72,13 @@ impl NativeMenu {
         }
     }
 
-    /// Dispatch clicked items and refresh state.
-    pub fn poll(&mut self, app: &mut VectorcraftApp) {
+    /// Dispatch chosen items (a focused text field takes Select All and the clipboard) and refresh
+    /// state.
+    pub fn poll(&mut self, app: &mut VectorcraftApp, ctx: &egui::Context) {
         while let Ok(ev) = MenuEvent::receiver().try_recv() {
             if let Some((cmd, params, _, _)) = self.items.get(ev.id.as_ref()) {
                 let p = if params.is_null() { serde_json::json!({}) } else { params.clone() };
-                menus::invoke(app, cmd, p);
+                menus::invoke_from_system_menu(app, ctx, cmd, p);
             }
         }
         let now = vectorcraft_ui_egui::now_ms();