test(ci): appease staticcheck nil guards

[jonathanhaaswriter]

Summary

• add explicit returns after nil-guard test failures that staticcheck cannot prove terminate execution
• quiet the current SA5011 false positives across actionengine and API tests
• unblock lint on the live-graph and store-backed follow-up PRs

Testing

• go test ./internal/actionengine ./internal/api -count=1
• python3 ./scripts/devex.py run --mode changed --base-ref writer/main

[jonathanhaaswriter]

Re-reviewed the current diff and I don't have any additional actionable findings right now.