Add MCP docs server to Claude Code GitHub Action

- Add .mcp.json with mcp-docs HTTP server configuration
- Update claude.yml to load MCP server config with --mcp-config
- Change --system-prompt to --append-system-prompt to preserve defaults
- Extend instructions to use mcp-docs for MCP-related work

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

.mcp.json

@@ -0,0 +1,8 @@
+{
+  "mcpServers": {
+    "mcp-docs": {
+      "type": "http",
+      "url": "https://modelcontextprotocol.io/mcp"
+    }
+  }
+}