Fix command-mode completion behavior when input is escaped

If `a\ b.txt` were a local file, `:o a\ <tab>` would fill the prompt
with `:o aa\ b.txt` because the replacement range was calculated using
the shellwords-parsed part. Escaping the part before calculating its
length fixes this edge-case.

helix-term/src/commands/typed.rs

@@ -2219,12 +2219,15 @@ pub(super) fn command_mode(cx: &mut Context) {
                     ..
                 }) = typed::TYPABLE_COMMAND_MAP.get(&command as &str)
                 {
+                    let part_len = shellwords::escape(part.clone()).len();
+
                     completer(editor, &part)
                         .into_iter()
                         .map(|(range, file)| {
                             let file = shellwords::escape(file);
+
                             // offset ranges to input
-                            let offset = input.len() - part.len();
+                            let offset = input.len() - part_len;
                             let range = (range.start + offset)..;
                             (range, file)
                         })