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 <noreply@anthropic.com>

crates/engine/src/cmd/select.rs

@@ -9,7 +9,15 @@ use super::*;
 
 pub fn specs() -> Vec<CommandSpec> {
     vec![
-        cmd!("select.all", "All", ["Select"], Some("Cmd+A"), "{}", has_doc, all),
+        cmd!(
+            "select.all",
+            "All",
+            ["Select"],
+            Some("Cmd+A"),
+            "{} → {count}; while the Type tool edits text, all of that text instead → {editing, start, end} (byte offsets)",
+            has_doc,
+            all
+        ),
         cmd!("select.allOnArtboard", "All on Active Artboard", ["Select"], Some("Cmd+Alt+A"), "{artboard?: index}", has_doc, all_on_artboard),
         cmd!("select.none", "Deselect", ["Select"], Some("Cmd+Shift+A"), "{}", has_doc, none),
         cmd!("select.reselect", "Reselect", ["Select"], Some("Cmd+6"), "{}", has_doc, reselect),
@@ -107,6 +115,18 @@ fn selectable(d: &Document, iso: Option<NodeId>) -> Vec<NodeId> {
 }
 
 fn all(s: &mut Session, _: &Value) -> Result<Value> {
+    // While the Type tool edits text, Select All takes all of that text and leaves the art
+    // selection as it is (Illustrator: text cursor in a text object).
+    if s.tool_wants_text() {
+        s.set_tool_option("selectAll", &json!(true));
+        let editing = s.tool_options()["editing"].clone();
+        let id = editing.as_u64().map(NodeId);
+        let end = id.and_then(|id| match &s.doc().ok()?.doc.node(id)?.kind {
+            NodeKind::Text(t) => Some(t.plain_text().len()),
+            _ => None,
+        });
+        return Ok(json!({ "editing": editing, "start": 0, "end": end.unwrap_or(0) }));
+    }
     let st = s.doc()?;
     let ids = selectable(&st.doc, st.isolation);
     s.select(|_, sel| sel.set(ids.iter().copied()))?;