feat(tui): support autocomplete trigger characters

closes #4703

packages/tui/src/autocomplete.ts

@@ -239,6 +239,9 @@ export interface AutocompleteSuggestions {
 }
 
 export interface AutocompleteProvider {
+	/** Characters that should naturally trigger this provider at token boundaries. */
+	triggerCharacters?: string[];
+
 	// Get autocomplete suggestions for current text/cursor position
 	// Returns null if no suggestions available
 	getSuggestions(