`resolve_owning_group`'s ancestor-chain CTE is the isolation boundary for EVERY
group shared collection — kv, docs, files, topics, queues. Its own doc says so.
Yet no test exercised the actual SQL: the tests that claimed to
(`unrelated_app_gets_collection_not_shared` in the three older group services,
`realtime_authority`'s SSE 404) inject a `FakeResolver` HashMap the test itself
populates — the foreign app resolves to `None` only because the test never
inserted it. They prove the service propagates a `None`; they cannot see the
query that produces it. Dropping `JOIN chain c ON gc.group_id = c.group_owner`
would let ANY app resolve ANY group's shared collection — a cross-tenant breach —
and the whole unit suite would stay green.
This drives the real query over a real tree: a descendant resolves, a
sibling-subtree app gets nothing, the kind filter is part of the boundary (a kv
and a docs collection of one name are distinct stores), nearest-declaration
shadows (security-relevant — a deep app must reach the nearer group's store), an
app-owned marker shares with nobody, and lookup is case-insensitive.
Mutation-verified: with the chain join dropped, the boundary assertion fires — and
under that breach `app_mid` resolves a FOREIGN group's `catalog` left in the DB by
another suite, i.e. the leak reproduces live.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
