fix: prevent text modification when Tab is pressed on execute-only completion items

Execute-only items (e.g., 'Browse files...') with an empty Value would
fall through to the text insertion logic, removing the trigger character
and inserting a space. Add a guard to close the popup cleanly instead.

Assisted-By: docker-agent

Author: dgageot

pkg/tui/components/editor/editor.go

@@ -672,8 +672,14 @@ func (e *editor) Update(msg tea.Msg) (layout.Model, tea.Cmd) {
 			return e, cmd
 		}
 
+		// Execute-only items (e.g., "Browse files...") with no value to insert:
+		// close the popup without modifying text when Tab is pressed.
+		if msg.Execute != nil && msg.Value == "" {
+			e.clearSuggestion()
+			return e, nil
+		}
 		// For non-auto-submit completions OR auto-submit with AutoExecute=false (Tab pressed),
-		// just insert the text without executing
+		// just insert the text without executing.
 		// This allows Tab to autocomplete command text without executing,
 		// so users can add arguments before pressing Enter to send
 		currentValue := e.textarea.Value()