Playwright cannot connect to localhost, must use 0.0.0.0

[magent-cryptograss]

When using Playwright MCP tools to navigate to the dev server, localhost:4000 results in net::ERR_CONNECTION_REFUSED but 0.0.0.0:4000 works.

This is likely a Docker networking or binding issue - the dev server binds to 0.0.0.0 but localhost resolution inside the container may not route correctly.

Workaround: Use 0.0.0.0:4000 instead of localhost:4000 for Playwright navigation.

To investigate:

• Check webpack-dev-server host binding configuration
• Verify /etc/hosts or DNS resolution inside container
• May be related to IPv4 vs IPv6 localhost resolution