perf: color variation CSS transient caching and Twig auto_reload fix (v1.0.9)

- functions.php: cache wp_bootstrap_variation_colors() output in a 24-hour
  transient keyed by md5(get_stylesheet()); invalidate on switch_theme and
  save_post_wp_global_styles so Design Editor changes apply immediately
- TwigService.php: change auto_reload from hardcoded true to WP_DEBUG so
  Twig stops stat()-ing compiled template files on every production request

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

functions.php

@@ -175,6 +175,17 @@ add_action( 'wp_enqueue_scripts', 'wp_bootstrap_rtl_styles', 20 );
  */
 if ( ! function_exists( 'wp_bootstrap_variation_colors' ) ) :
     function wp_bootstrap_variation_colors() {
+        $transient_key = 'wp_bootstrap_variation_css_' . md5( get_stylesheet() );
+        $cached_css    = get_transient( $transient_key );
+
+        if ( false !== $cached_css ) {
+            // '' means default palette (no inline CSS needed); non-empty string is the computed CSS.
+            if ( '' !== $cached_css ) {
+                wp_add_inline_style( 'wp-bootstrap-style', $cached_css );
+            }
+            return;
+        }
+
         // Read the theme origin palette — this contains the base theme.json
         // colors merged with the active style variation (if any).
         $theme_palette = wp_get_global_settings( array( 'color', 'palette', 'theme' ) );
@@ -205,10 +216,12 @@ if ( ! function_exists( 'wp_bootstrap_variation_colors' ) ) :
 
         // No variation active — let Bootstrap's compiled CSS handle both modes.
         if ( $is_default ) {
+            set_transient( $transient_key, '', DAY_IN_SECONDS );
             return;
         }
 
         if ( empty( $colors['base'] ) || empty( $colors['contrast'] ) ) {
+            set_transient( $transient_key, '', DAY_IN_SECONDS );
             return;
         }
 
@@ -280,6 +293,9 @@ if ( ! function_exists( 'wp_bootstrap_variation_colors' ) ) :
              . '[data-bs-theme=light]{' . $light_css . '}'
              . '[data-bs-theme=dark]{' . $dark_css . '}';
 
+        // Cache for 24 hours; invalidated on theme switch or global-styles save.
+        set_transient( $transient_key, $css, DAY_IN_SECONDS );
+
         // Attach after the compiled stylesheet so variation values override
         // Bootstrap's hardcoded dark-mode defaults via source order.
         wp_add_inline_style( 'wp-bootstrap-style', $css );
@@ -287,6 +303,16 @@ if ( ! function_exists( 'wp_bootstrap_variation_colors' ) ) :
 endif;
 add_action( 'wp_enqueue_scripts', 'wp_bootstrap_variation_colors', 30 );
 
+/**
+ * Invalidate the color variation CSS transient when global styles or theme change.
+ */
+add_action( 'switch_theme', function () {
+    delete_transient( 'wp_bootstrap_variation_css_' . md5( get_stylesheet() ) );
+} );
+add_action( 'save_post_wp_global_styles', function () {
+    delete_transient( 'wp_bootstrap_variation_css_' . md5( get_stylesheet() ) );
+} );
+
 /**
  * Build Bootstrap surface CSS variables for a given background/foreground pair.
  *