Preserve caller browser artifact schemas

[chubes4]

Summary

• Removes the Studio Web-specific browser artifact bundle schema gate from generated runner capture.
• Captures any non-empty caller-provided artifact schema while preserving opaque caller roles and metadata.
• Extends the WordPress plugin smoke test with a non-Studio caller schema, invalid path skip, unreadable file skip, and missing-entrypoint coverage.

Tests

• php tests/smoke-wordpress-plugin.php
• npm run build

AI assistance

• AI assistance: Yes
• Tool(s): OpenCode (gpt-5.5)
• Used for: Drafted the code change and smoke coverage; Chris remains responsible for review and testing.