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).

ARCHITECTURE.md

@@ -47,6 +47,8 @@ peptide-starter/
 │   ├── newsletter-admin.php       # Subscriber viewer + CSV-safe export +
 │   │                               # /newsletter-unsubscribe route.
 │   ├── mail-diagnostic.php        # [v1.5.1] Tools → Mail Test — wp_mail probe.
+│   ├── perf-asset-policy.php      # [v1.6.0] Mobile perf: dequeue + font slim
+│   │                               # + preconnect + defer.
 │   └── page-setup.php             # Auto-create pages on activation +
 │                                    # v1.5.0 user migration (enrol into verify).
 │
@@ -265,7 +267,7 @@ for out-of-band updates.
 
 ## Version
 
-**Current:** v1.5.2 (2026-04-14)
+**Current:** v1.6.0 (2026-04-23)
 
 Bump `style.css` header line 7 and `PEPTIDE_STARTER_VERSION` in
 `functions.php` together on release.