vim: Don't show inline completions in normal mode (#17137)

This fixes an annoying bug I ran into, where supermaven completions
would show up in normal mode.

cc @ConradIrwin not sure if this is the best way to fix this, but it
seems like the neatest? On one hand, I didn't want to touch into Vim
from the editor, and on the other I didn't want to add another boolean
on the editor that flips on when in normal mode. So instead I extended
the Addon interface.

Release Notes:

- Fixed inline completions (Copilot or Supermaven) showing up in Vim's
normal mode.

crates/vim/src/vim.rs

@@ -91,8 +91,7 @@ pub fn init(cx: &mut AppContext) {
     VimSettings::register(cx);
     VimGlobals::register(cx);
 
-    cx.observe_new_views(|editor: &mut Editor, cx| Vim::register(editor, cx))
-        .detach();
+    cx.observe_new_views(Vim::register).detach();
 
     cx.observe_new_views(|workspace: &mut Workspace, _| {
         workspace.register_action(|workspace, _: &ToggleVimMode, cx| {
@@ -135,6 +134,11 @@ impl editor::Addon for VimAddon {
         self.view.read(cx).extend_key_context(key_context)
     }
 
+    fn should_show_inline_completions(&self, cx: &AppContext) -> bool {
+        let mode = self.view.read(cx).mode;
+        mode == Mode::Insert || mode == Mode::Replace
+    }
+
     fn to_any(&self) -> &dyn std::any::Any {
         self
     }