Add architecture docs and fork maintenance strategy (#6)

Document channel architecture, M3U/XMLTV integration with Jellyfin,
and fork maintenance strategy for the archived upstream. Also includes
CLAUDE.md updates for implementer workflow and project boundaries.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.mcp.json

@@ -48,7 +48,9 @@
         "--source", "https://api.nuget.org/v3/index.json",
         "--yes"
       ],
-      "env": {}
+      "env": {
+        "DOTNET_ROOT": "/usr/local/share/dotnet"
+      }
     }
   }
 }