Branch protection and source-control write scoping.

No branch protection; agents (and humans) can push directly to `main`; the PR review gate (`PL2-external-pr-review`) is procedural only

Branch protection enabled on `main` but inconsistently applied across repos or branches (e.g. `develop` unprotected); approval requirement exists but bypassable by repo admins without audit

All protected branches locked across every repo: direct push blocked; merge requires at least one human approval OR an audited automated-merge rule; branches must be current with target at merge time (platform "require up to date before merging" OR merge queue that rebases and tests before merge); bypass requires explicit override with audit log. Agents are scoped to feature branches by platform-enforced rules, not convention