Summary

• Adds a separate feature control for external-browser Browser Use integrations.
• Registers browser_use_external as a stable, default-enabled requirements-owned feature key.
• Updates feature registry tests and regenerates the config schema.

Codex validation:

• cargo fmt -- --config imports_granularity=Item
• cargo run -p codex-core --bin codex-write-config-schema
• cargo test -p codex-features

Addendum

This gives enterprise policy a coarse control for Browser Use outside the Codex-managed in-app browser. The existing browser_use feature is the Browser Use control, while browser_use_external can gate extension/native integrations for external browsers as that surface grows