feat(ui): feature-parity context menu — Snap Overrides, transparent Pan/Zoom, ARC keyword flow

The command menu now follows the commercial solutions' layout row for row: Enter, Cancel,
Recent Input ▸, the command's keywords, Snap Overrides ▸ (every object snap
with its glyph, Mid Between 2 Points, None, Osnap Settings…), then Pan and
Zoom. Pan / Zoom run transparently while a command is active ('PAN,
'ZOOM …): navigation modes leave the command untouched and an interactive
ZOOM Window parks it and resumes it afterwards. Rows carry an icon gutter
so labels align; the Enter row shows a default value ("<0.5000>") as its
hint instead of a second finish row.

ARC gets the commercial solutions' prompt flow with all keywords: start [Center], second
point [Center/End], end; after Center: end [Angle/chord Length]; after
End: center [Angle/Direction/Radius]; Enter continues tangent. The
previous default (Center/Start/End with method codes) stays as ARC_CSE.

Object snaps gain a one-shot "None" override. New strings in all locales.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/app/commands/draw.rs

@@ -311,8 +311,8 @@ impl OpenCADStudio {
             }
 
             "ARC" => {
-                use crate::modules::draw::draw::arc::Arc3PCommand;
-                let new_cmd = Arc3PCommand::new();
+                use crate::modules::draw::draw::arc::ArcCommand;
+                let new_cmd = ArcCommand::new();
                 self.command_line.push_info(&new_cmd.prompt());
                 self.tabs[i].active_cmd = Some(Box::new(new_cmd));
             }
@@ -323,8 +323,8 @@ impl OpenCADStudio {
                 self.tabs[i].active_cmd = Some(Box::new(new_cmd));
             }
             "ARC_CSE" => {
-                use crate::modules::draw::draw::arc::ArcCommand;
-                let new_cmd = ArcCommand::new();
+                use crate::modules::draw::draw::arc::ArcCSECommand;
+                let new_cmd = ArcCSECommand::new();
                 self.command_line.push_info(&new_cmd.prompt());
                 self.tabs[i].active_cmd = Some(Box::new(new_cmd));
             }