fix(autocomplete): Sync last_filter en setText/clear + auto-cierre dropdown vacío

Cambios de Gemini para estabilidad IMGUI:
- setText(): Sincroniza last_filter para evitar falsos text_changed
- clear(): Resetea last_filter_len
- autocompleteRect(): Cierra dropdown si options.len == 0

Parte de la solución para corrupción de memoria en cascade AutoComplete.

src/widgets/autocomplete.zig

@@ -59,6 +59,10 @@ pub const AutoCompleteState = struct {
         @memcpy(self.buffer[0..copy_len], new_text[0..copy_len]);
         self.len = copy_len;
         self.cursor = copy_len;
+
+        // Sync filter to avoid spurious text_changed events
+        @memcpy(self.last_filter[0..copy_len], new_text[0..copy_len]);
+        self.last_filter_len = copy_len;
     }
 
     /// Clear the input
@@ -68,6 +72,7 @@ pub const AutoCompleteState = struct {
         self.selected = -1;
         self.highlighted = -1;
         self.open = false;
+        self.last_filter_len = 0;
     }
 
     /// Insert a single character at cursor
@@ -403,6 +408,9 @@ pub fn autocompleteRect(
     var filtered_indices: [256]usize = undefined;
     var filtered_count: usize = 0;
 
+    if (options.len == 0) {
+        state.closeDropdown();
+    } else {
         for (options, 0..) |opt, i| {
             if (filtered_count >= filtered_indices.len) break;
             if (matchesFilter(opt, filter_text, config.match_mode, config.case_sensitive)) {
@@ -410,6 +418,7 @@ pub fn autocompleteRect(
                 filtered_count += 1;
             }
         }
+    }
 
     // Handle keyboard input when focused
     if (is_focused and !config.disabled) {