feat: add MCP server package for npx distribution (#284)

* feat: add MCP server package for npx distribution

- Self-contained MCP server with embedded HTTP server
- Real-time browser preview via draw.io iframe
- Tools: start_session, display_diagram, edit_diagram, get_diagram, export_diagram
- Port retry limit (6002-6020) and session TTL cleanup (1 hour)
- Published as @next-ai-drawio/mcp-server on npm

* chore: bump version to 0.1.2

* docs: add MCP server section to README (preview feature)

* docs: add multi-client installation instructions for MCP server

* fix: exclude packages from Next.js build

* docs: use @latest instead of -y flag for npx (match Playwright MCP style)

* chore: bump version to 0.4.3 and add release notes

* chore: remove release notes

* feat: add MCP server notice to example panel

packages/mcp-server/src/logger.ts

@@ -0,0 +1,24 @@
+/**
+ * Logger for MCP server
+ *
+ * CRITICAL: MCP servers communicate via STDIO (stdin/stdout).
+ * Using console.log() will corrupt the JSON-RPC protocol messages.
+ * ALL logging MUST use console.error() which writes to stderr.
+ */
+
+export const log = {
+    info: (msg: string, ...args: unknown[]) => {
+        console.error(`[MCP-DrawIO] [INFO] ${msg}`, ...args)
+    },
+    error: (msg: string, ...args: unknown[]) => {
+        console.error(`[MCP-DrawIO] [ERROR] ${msg}`, ...args)
+    },
+    debug: (msg: string, ...args: unknown[]) => {
+        if (process.env.DEBUG === "true") {
+            console.error(`[MCP-DrawIO] [DEBUG] ${msg}`, ...args)
+        }
+    },
+    warn: (msg: string, ...args: unknown[]) => {
+        console.error(`[MCP-DrawIO] [WARN] ${msg}`, ...args)
+    },
+}