In-suite belt-and-braces detector for the birpc teardown race named in
ADR-012 / #553. Catches `vi.mock(<arg>, async ... { ... await import(...)
... })` in any browser spec on every vitest invocation — the layer hardest
to disable or scope around (ESLint can be silenced; CI grep runs only in
CI; this test runs whenever the suite runs).
Demonstrated red→green by planting a synthetic offender locally and
watching the live-scan assertion fail; removing the offender returned it
to green.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>