feat(commandline): always-on keyboard capture + space submits like enter

Two behaviour changes that bring the command line in line with
established CAD workflow:

1. **Always-on keyboard capture.** The input was blurred whenever no
   command was running, so typed letters went nowhere until the user
   clicked into the field. Replace the blur with a re-focus on every
   command lifecycle transition (cmd_result.rs) and on viewport / tab
   / ribbon clicks (update.rs), focus the input at startup, and add
   a global key subscription that catches any unhandled character key
   or backspace and routes it into the buffer via two new messages
   (CommandAppendChar / CommandBackspace) — so the command line keeps
   accumulating keystrokes even if focus parks somewhere not
   focusable. Removes the unused blur_cmd_input helper.

2. **Space submits.** Typing a space at the end of the input now
   submits the buffer the same way Enter does. Only exception: an
   active command that's currently collecting free-form prose
   (TEXT / MTEXT / DDEDIT body, ATTDEF prompt / default value,
   INSERT attribute value, ATTEDIT cell). Those advertise the new
   `CadCommand::wants_text_with_spaces()` flag so the Space character
   reaches the buffer as a literal.

Co-Authored-By: Claude Opus 4.7 <[email protected]>

src/ui/ribbon/widgets.rs

@@ -359,7 +359,7 @@ pub(super) fn render_small<'a>(
                 .height(ROW_H)
                 .padding([4, 4]);
 
-            let arr_tip = format!("{} seçenekleri", cur_label);
+            let arr_tip = format!("{} options", cur_label);
             let arr_btn = button(
                 container(text("▾").size(7).color(ARROW_COLOR))
                     .width(Fill)
@@ -488,7 +488,7 @@ pub(super) fn render_large<'a>(
                 .or_else(|| items.first().map(|(_, lbl, _)| *lbl))
                 .unwrap_or(label);
             let tip_text = format!("{}\nCommand: {}", cur_label, last);
-            let arr_tip = format!("{} seçenekleri", label);
+            let arr_tip = format!("{} options", label);
 
             let top_btn = button(
                 column![