Add Claude Desktop extensions (.mcpb) for WordCraft and GridCraft.

Ship unsigned MCPB packages built from the ArtCraft Launcher CLIs, with install docs and skill 0.2.0 updates.

skills/gridcraft-mcp/extension/LICENSES/NOTICE

@@ -0,0 +1,16 @@
+GridCraft
+Copyright (c) 2026 ArtCraft Team and the GridCraft contributors.
+Licensed under the MIT License or the Apache License, Version 2.0, at your option
+(LICENSE-MIT, LICENSE-APACHE).
+
+The ArtCraft name, wordmark and logos in docs/brand/ are trademarks of the ArtCraft Team. They are
+not open source and are not covered by the license above; their terms are in
+docs/brand/LICENSE-brand.txt.
+
+Third-party material
+
+This product bundles third-party material under its own licenses, listed below. The per-file
+list (author, source, license) is in ATTRIBUTION.md.
+
+None: every bundled asset is original to GridCraft. Builds made with craft-fonts
+(CRAFT_FONTS_DIR) embed the fonts listed in ATTRIBUTION.md under the SIL Open Font License 1.1.