feat(voyage): scaffold playground/ with DS vendor sync — v4.2 Step 5

- playground/voyage-playground.html: minimal skeleton (DOCTYPE, app-header, guide-panel, aria-live region, skip-to-main link). Steps 8-11 will extend with render-pipeline + creation gestures + sidebar + export.
- playground/vendor/playground-design-system/: synced via 'node scripts/sync-design-system.mjs voyage' (27 files + MANIFEST.json with source_commit + sync_date + SHA-256 per file).
- tests/playground/voyage-playground.test.mjs: 8 tests pinning HTML existence, DOCTYPE, no-external-URLs, no-marked, A11Y skip-to-main + aria-live, MANIFEST.json structure, vendored DS files present.
- shared/PLAYGROUND-MAINTENANCE.md: consumer list updated 5 -> 6 (added voyage).

plugins/voyage/playground/vendor/playground-design-system/fonts.css

@@ -0,0 +1,84 @@
+/* Code generated by sync-design-system.mjs; DO NOT EDIT. */
+/*
+ * Self-hosted web fonts for Playground Design System.
+ *
+ * All three families are licensed under SIL Open Font License 1.1.
+ * Full license text and provenance: ./fonts/LICENSES.md
+ *
+ * Why self-hosted:
+ *   - No external requests (no fonts.googleapis.com, no IP/UA leakage).
+ *   - Works offline / behind air-gapped firewalls.
+ *   - GDPR-compliant for Norwegian public-sector deployments.
+ *
+ * Bundle size: ~940 KB total across 9 woff2 files.
+ * Loaded via font-display: swap to avoid FOIT.
+ */
+
+/* ========== Inter (UI / body) ========== */
+@font-face {
+  font-family: "Inter";
+  font-style: normal;
+  font-weight: 400;
+  font-display: swap;
+  src: url("./fonts/Inter-Regular.woff2") format("woff2");
+}
+@font-face {
+  font-family: "Inter";
+  font-style: normal;
+  font-weight: 500;
+  font-display: swap;
+  src: url("./fonts/Inter-Medium.woff2") format("woff2");
+}
+@font-face {
+  font-family: "Inter";
+  font-style: normal;
+  font-weight: 600;
+  font-display: swap;
+  src: url("./fonts/Inter-SemiBold.woff2") format("woff2");
+}
+@font-face {
+  font-family: "Inter";
+  font-style: normal;
+  font-weight: 700;
+  font-display: swap;
+  src: url("./fonts/Inter-Bold.woff2") format("woff2");
+}
+
+/* ========== JetBrains Mono (code) ========== */
+@font-face {
+  font-family: "JetBrains Mono";
+  font-style: normal;
+  font-weight: 400;
+  font-display: swap;
+  src: url("./fonts/JetBrainsMono-Regular.woff2") format("woff2");
+}
+@font-face {
+  font-family: "JetBrains Mono";
+  font-style: normal;
+  font-weight: 500;
+  font-display: swap;
+  src: url("./fonts/JetBrainsMono-Medium.woff2") format("woff2");
+}
+@font-face {
+  font-family: "JetBrains Mono";
+  font-style: normal;
+  font-weight: 600;
+  font-display: swap;
+  src: url("./fonts/JetBrainsMono-SemiBold.woff2") format("woff2");
+}
+
+/* ========== Source Serif 4 (occasional editorial accents) ========== */
+@font-face {
+  font-family: "Source Serif 4";
+  font-style: normal;
+  font-weight: 400;
+  font-display: swap;
+  src: url("./fonts/SourceSerif4-Regular.woff2") format("woff2");
+}
+@font-face {
+  font-family: "Source Serif 4";
+  font-style: normal;
+  font-weight: 600;
+  font-display: swap;
+  src: url("./fonts/SourceSerif4-Semibold.woff2") format("woff2");
+}