test(ci): match workflow-runner-labels to the github-hosted validation move

[JSONbored]

Summary

• #2825 moved validate-code (ci.yml) and the scheduled audit job (audit.yml) from the self-hosted [self-hosted, gittensory] runner pool to ubuntu-latest while the self-hosted review stack is CPU constrained, but didn't update test/unit/workflow-runner-labels.test.ts, which still asserted the old self-hosted-pool expectations.
• That leaves main with a failing unit test right now, which would block npm run test:ci (and the validate required check) for any unrelated PR cut from current main.
• Rewrites the drift guard to assert the new invariant instead of the old one: every runs-on: line in ci.yml/audit.yml stays on ubuntu-latest, none select the self-hosted pool. selfhost.yml's own (unrelated, untouched) assertions are unchanged.

Scope

• Test-only change (test/unit/workflow-runner-labels.test.ts), no src/** touched — no Codecov patch-coverage obligation.
• No secrets, wallet/hotkey/trust/reward terms anywhere.
• In wantedPaths, narrow, single concern.

Validation

• npm run typecheck
• npx vitest run test/unit/workflow-runner-labels.test.ts (3/3 passing)
• npx vitest run test/unit/check-migrations-script.test.ts test/unit/check-schema-drift-script.test.ts (unrelated pre-existing failures in the same full-suite run, traced to a stale node_modules/.bin/tsx in this worktree, not this change; resolved by npm ci, unaffected by this diff)
• npm audit --audit-level=moderate (0 vulnerabilities)
• git diff --check (clean)

Safety

• No auth/CORS/session paths touched.
• No secrets committed.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
⚠️ Please upload report for BASE (main@1748db8). Learn more about missing BASE report.
⚠️ Report is 3 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2827   +/-   ##
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  Coverage        ?   96.20%           
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  Files           ?      253           
  Lines           ?    27781           
  Branches        ?    10093           
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  Hits            ?    26726           
  Misses          ?      433           
  Partials        ?      622           

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