runtime: DisposableStack / Symbol.dispose surface incomplete (.disposed returns undefined)

[proggeramlug]

Summary

DisposableStack / Symbol.dispose support is incomplete: test_gap_disposablestack_2875 returns undefined where node returns false / true.

This is an untriaged gap-suite failure on main — it is not in test-parity/known_failures.json.

Repro

test-files/test_gap_disposablestack_2875.ts on current main (be5ed2bfc) vs node --experimental-strip-types:

line 5:   perry: undefined     node: false
line 7:   perry: undefined     node: true

Looks like the .disposed getter (and/or the adopt/defer surface) is missing rather than the whole feature.

Why CI never caught it

DisposableStack and Symbol.dispose are Node 24+. conformance-smoke pins node-version: '22' (.github/workflows/test.yml), where node itself fails the test — so the harness classifies it as node_fail and excludes it entirely. The gap is structurally invisible to the required gate.

That is the more important point: this issue is a symptom. Anything Perry gets wrong about a Node 24/26 feature cannot be seen by CI at all, by construction. Tracked separately as the Node-version skew issue.

Decision needed

Either implement the missing surface, or add a triaged entry to test-parity/known_failures.json with a category and reason — right now it sits in the gap that the no-new-untriaged gate exists to prevent.