[Docs]: Bind core/Lab isolation and synchronous activation in the invariant index #5121

Documentation problem type

Incorrect documentation

Documentation location

structure/overview.md:90, structure/adapters/compatibility-lab.md, tests/lab/core-lab-boundary.test.ts

What is wrong or missing?

The root agent guidance declares core/Lab import isolation and synchronous activation non-negotiable, and a transitive mutation-tested guard exists, but the overview invariant index has no corresponding stable binding. tests/lab/core-lab-boundary.test.ts:20 and tests/lab/core-lab-boundary.test.ts:991 already own enforcement.

What should the documentation explain instead?

Add a stable invariant ID tying both guarantees to the existing guard, with a backlink in the test and a link from the Lab contract document. Preserve the guard and its current negative coverage.

Suggested wording or example

“INV-LAB-01: the protected core entrypoints cannot reach optional Lab runtime imports; gated Lab activation remains synchronous before startServer returns.” Check that this ID is unused before implementation.

Additional context or attachments

Pinned source: 7864869c31c41cca9830d93540238f17df8faafb. Static documentation/source comparison only; no runtime test result is claimed.

Update structure/overview.md, structure/adapters/compatibility-lab.md and an existing test comment/describe label. Use the existing invariant binding checker and focused guard in implementation; no new runtime mechanism is needed. Closed #4704 hardened the guard, not this documentation binding.

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