feat(perf): mobile performance Phase 1 — dequeue unused plugin assets + slim fonts + preconnect (#13)

Ships peptide-starter-theme v1.6.0.

Changes:
- New inc/perf-asset-policy.php module: conditional dequeue of WC/Elementor/USMI assets on pages that do not need them, Google Fonts weight slim (Roboto 100..900 → 400/500/700; Roboto Slab → 400/700), wp_resource_hints preconnect for fonts.googleapis.com + fonts.gstatic.com, cookie-notice-front script defer.
- Kill-switch constant PEPTIDE_STARTER_PERF_DEQUEUE (default true) for instant rollback via wp-config.php.
- 4 extensibility filters: peptide_starter_perf_woocommerce_{styles,scripts}, _elementor_{styles,scripts}, _usmi_{styles,scripts}, _font_weights.
- 13 unit tests in tests/test-perf-asset-policy.php.
- Bootstrap: 2 lines in functions.php (require + after_setup_theme action).
- Docs: CHANGELOG [1.6.0], ARCHITECTURE.md, CONVENTIONS.md how-to.

Target: mobile PSI 74 → 90+, LCP 5.4s → ~2.5s.

Post-deploy: purge LiteSpeed CSS bundle.

QA: qa-reviews/peptide-starter-theme/2026-04-23-a54b5c9.md (APPROVE with handle-drift verified false-positive).

functions.php

@@ -15,6 +15,7 @@
  * @see inc/page-setup.php       — auto-create pages + v1.5.0 user migration
  * @see inc/mail-diagnostic.php  — admin deliverability test tool
  * @see inc/helpers.php          — nav walker, menu fallback, gates, utilities
+ * @see inc/perf-asset-policy.php — asset dequeue + font slim + preconnect + defer
  *
  * @package peptide-starter
  */
@@ -25,7 +26,7 @@ if ( ! defined( 'ABSPATH' ) ) {
 }
 
 // Theme constants.
-define( 'PEPTIDE_STARTER_VERSION', '1.5.2' );
+define( 'PEPTIDE_STARTER_VERSION', '1.6.0' );
 define( 'PEPTIDE_STARTER_DIR', get_template_directory() );
 define( 'PEPTIDE_STARTER_URI', get_template_directory_uri() );
 
@@ -42,6 +43,7 @@ require_once PEPTIDE_STARTER_DIR . '/inc/contact-handler.php';
 require_once PEPTIDE_STARTER_DIR . '/inc/page-setup.php';
 require_once PEPTIDE_STARTER_DIR . '/inc/newsletter-admin.php';
 require_once PEPTIDE_STARTER_DIR . '/inc/mail-diagnostic.php';
+require_once PEPTIDE_STARTER_DIR . '/inc/perf-asset-policy.php';
 
 /**
  * Set up theme defaults and register support for WordPress features.
@@ -69,6 +71,7 @@ function peptide_starter_setup() {
 	load_theme_textdomain( 'peptide-starter', PEPTIDE_STARTER_DIR . '/languages' );
 }
 add_action( 'after_setup_theme', 'peptide_starter_setup' );
+add_action( 'after_setup_theme', 'peptide_starter_perf_asset_policy_init' );
 
 /**
  * Register and enqueue stylesheets and scripts.