Fix local browser runtime package delivery

[chubes4]

Summary

• Normalize WP Codebox-generated loopback browser runtime package URLs from http://127.0.0.1 / http://[::1] to http://localhost before emitting stable URL delivery.
• Preserve URL delivery for packages above the inline data URL budget so browser session payloads do not embed large ZIP data URLs.
• Add smoke coverage for forced URL delivery from a local upload base URL and assert the emitted blueprint uses the localhost package URL.

Fixes #410.

Tests

• npm run wordpress-plugin-smoke
• npm run build

AI assistance

• AI assistance: Yes
• Tool(s): OpenCode (GPT-5.5)
• Used for: Diagnosing the browser runtime package transport failure, implementing the WP Codebox upstream fix, and adding targeted smoke coverage; Chris remains responsible for review and merge.