feat(fix-workflow): decide on auto-merge vs human-review for CoCo fix PRs

[sfc-gh-ksampath]

Context

The cortex-fix.yml workflow currently runs gh pr merge --squash --auto --delete-branch
immediately after creating the fix PR. This means AI-generated security/bug fixes can
land in main with no human review if branch protection rules allow it.

The question

Should the scaffold default to:

1. Open PR only — remove --auto, human reviews and merges. Safest.
   Suitable for: security fixes, logic changes, any multi-file patch.

2. Auto-merge with score threshold — only auto-merge if the fix is
   low-risk (single file, small diff, high-confidence scan result).
   Requires scoring/classification logic in the workflow.

3. Draft PR — open as draft by default, forcing conscious human
   promotion before merge is possible.

4. Configurable — scaffold asks during step 4 which policy the user wants.
   Store in manifest, write to workflow env var.

Current leaning

Option 1 (open PR only) as the safe default. Auto-merge can be an opt-in
for users who understand the risk and have sufficient branch protection and CI
checks in place to gate it.

Related

• can_approve_pull_request_reviews permission (separate from PR creation)
• Branch protection rule timing (see companion issue/discussion)
• Step 4 sets default_workflow_permissions=write to enable PR creation