ep: Only report shown once prediction is previewed in subtle mode (#52362)

## Context

We currently mark the current prediction as "shown" when the subtle mode
indicator appears. This doesn't really make sense. We make an effort
elsewhere to differentiate between a user rejecting a prediction that
they viewed vs. never saw in order to compute accurate metrics.

## Self-Review Checklist

<!-- Check before requesting review: -->
- [x] I've reviewed my own diff for quality, security, and reliability
- [x] Unsafe blocks (if any) have justifying comments
- [x] The content is consistent with the [UI/UX
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
- [x] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable

Release Notes:

- N/A or Added/Fixed/Improved ...

crates/editor/src/editor.rs

@@ -8842,6 +8842,7 @@ impl Editor {
             let target = first_edit_start;
             EditPrediction::MoveWithin { target, snapshot }
         } else {
+            let show_completions_in_menu = self.has_visible_completions_menu();
             let show_completions_in_buffer = !self.edit_prediction_visible_in_cursor_popover(true)
                 && !self.edit_predictions_hidden_for_vim_mode;
 
@@ -8855,16 +8856,26 @@ impl Editor {
                 EditDisplayMode::DiffPopover
             };
 
-            if show_completions_in_buffer {
-                if let Some(provider) = &self.edit_prediction_provider {
-                    let suggestion_display_type = match display_mode {
-                        EditDisplayMode::DiffPopover => SuggestionDisplayType::DiffPopover,
-                        EditDisplayMode::Inline | EditDisplayMode::TabAccept => {
-                            SuggestionDisplayType::GhostText
-                        }
-                    };
-                    provider.provider.did_show(suggestion_display_type, cx);
+            let report_shown = match display_mode {
+                EditDisplayMode::DiffPopover | EditDisplayMode::Inline => {
+                    show_completions_in_buffer || show_completions_in_menu
                 }
+                EditDisplayMode::TabAccept => {
+                    show_completions_in_menu || self.edit_prediction_preview_is_active()
+                }
+            };
+
+            if report_shown && let Some(provider) = &self.edit_prediction_provider {
+                let suggestion_display_type = match display_mode {
+                    EditDisplayMode::DiffPopover => SuggestionDisplayType::DiffPopover,
+                    EditDisplayMode::Inline | EditDisplayMode::TabAccept => {
+                        SuggestionDisplayType::GhostText
+                    }
+                };
+                provider.provider.did_show(suggestion_display_type, cx);
+            }
+
+            if show_completions_in_buffer {
                 if edits
                     .iter()
                     .all(|(range, _)| range.to_offset(&multibuffer).is_empty())