chore: add project .mcp.json for dev server

Run the MCP server from src via tsx so the in-repo client always
uses current source. Avoids the stale/ missing dist trap from bare
`npx dbmole-mcp` resolving the local package in this folder.

.mcp.json

@@ -0,0 +1,9 @@
+{
+  "mcpServers": {
+    "dbmole": {
+      "type": "stdio",
+      "command": "npx",
+      "args": ["-y", "tsx", "src/index.ts"]
+    }
+  }
+}