fix(authz): the connector owner routes require listed membership, not just createdBy (TASK-168)

[lilyshen0722]

Cut from f77c18e5 (main after #1943). Backend only, no version bump.

Cleared by @vera at 358427ac (74705): each of the six sites reddens its own arm alone, lint 0 errors and 0 on any touched line. Body-only edits since — head unchanged.

The defect

createdBy records who made the pod and survives leavePod — leaving filters members, not the field. Five owner routes gated on the field alone:

route	what it exposed
POST /:id/connect	re-attach the pod's channel
POST /:id/disconnect	tear the pod's channel down
GET /:id/stats	the channel's telemetry
GET /:id/messages	read the pod's Discord channel (DiscordService.fetchMessages)
POST /:id/send	post into the pod's Discord channel (DiscordService.sendMessage)

After TASK-161/162 closed every relay and chat path to a departed creator, these five still answered to one — the same hole, through a route that calls no predicate at all, which is also why #1940's census walked past them.

canDeleteIntegration had the same shape on its pod-creator arm, and that function is the write gate for six further call sites (both ingest-token routes, the connect code, the PATCH, and DELETE).

The fix

isListedPodMember(pod, callerId) beside the creator check at each of the five routes, and on canDeleteIntegration's pod-creator arm. No new import, and no new spelling to pick wrong: this file already imports the strict rule at line 38 — require('../services/connectorRelayPolicy'), which re-exports utils/isPodMember's strict rule and says why in its own header ("every connector site reads one definition through this module"). The row's spec pointed at utils/isPodMember; that is where the rule is defined, and this file reaches it through the connector layer's re-export. The admin and integration-creator arms are untouched: neither ever claimed pod membership.

Why the exposure is exactly "a creator who left"

models/Pod.ts:194 pushes createdBy into members for every new pod, so a pod's creator is listed from birth and createdBy ∉ members means they left. That is what makes this shape a defect rather than a tautology — and it caught my first version of the arms, which declared members: [bystander] on a creator's pod and passed without ever reaching the predicate: the hook silently repaired the fixture into a listed creator. The fixtures now $pull the creator after creation, which is what leavePod does and which the hook's isNew guard leaves alone. A future author adding an arm here will hit the same trap; it is commented in the test file.

Exposure count — zero today, measured from both directions

Vera ran it on live Mongo, which my lane cannot reach: 59 pods whose creator is not in members, carrying 0 integrations, and of the 14 integration rows, 13 have a podId and 0 of those point at an unlisted creator's pod. Latent, like TASK-164 — the routes are unreachable for the population that exists today, and the two-directional census is what makes that a measurement rather than a hope. (Query asked of Vera: pods where createdBy is absent from members ∩ active integrations, grouped by type.)

"A creator no longer listed" — not "a creator who left"

My build note argued that models/Pod.ts:194 (the pre-save hook that pushes createdBy into members on every new pod) makes createdBy ∉ members mean the creator left. @vera corrected the reason, and it matters for scope: leavePod has no client caller (wren, 74691), so the 59 pods we measured were not produced by leaving. They were produced by the agent-side removals — agentIdentityService.ts:710 and agentInstallationCleanupService.ts:299 $pull an agent user, plus three one-shot bot migrations — consistent with all 29 unlisted creators being bots. The leavePod guard (#1945) bounds the human set at one; the bot set keeps being produced by agent cleanup, guard or no guard. So the guard is right and it is not what protects these five routes: the membership read is, which is why it sits on every pod-creator arm rather than on the leave path.

The direction this fix fails in silently

All six sites call Pod.findById(...) with no select, and isListedPodMember needs pod.members — but the TS cast on those lines types the document as { createdBy?: … } only. A future reader "tightening" that to .select('createdBy') would refuse every creator, listed or not, at all five routes. @vera applied exactly that projection to the messages route and it reddened a listed creator is unaffected: all five owner routes still act, so the requirement is witnessed by a control rather than by a refusal arm. If you are editing one of those casts, that arm is the one that will tell you.

Witnesses

Nine arms, real Pod/Integration/User rows on memory Mongo. The two proxy routes assert the side effect did not happen (fetchMessages / sendMessage not called), not only the status — a 403 reached after the call would be no fix at all.

#	arm	red
M1	/:id/connect added term removed	refuses /connect … and never connects
M2	/:id/disconnect term removed	refuses /disconnect … and never disconnects
M3	/:id/stats term removed	refuses /stats … and never reads stats
M4	/:id/messages term removed	refuses /messages … and never reads the channel
M5	/:id/send term removed	refuses /send … and never posts to the channel
M6	canDeleteIntegration pod arm term removed	refuses DELETE for a pod creator who is no longer listed, and removes nothing
M7	canDeleteIntegration integration-creator arm removed (control liveness)	the integration-creator arm is untouched: a departed pod creator who created the connector still deletes it
M8	seam: the shared predicate regains its creator clause	all six refusal arms, 3 controls still green

Every mutation ran alone and reddened exactly its named arm — no survivors. Two are controls rather than site mutations and are labelled as such: M7 proves the third arm is what admits the handover case, so my "untouched" claim is witnessed rather than asserted; M8 mutates the shared rule instead of a call site, which is why it reddens six arms at once and is expected to.

Three control arms keep the refusals honest: a listed creator still acts on all five routes (one arm walking all five), a listed pod creator still deletes a connector someone else made, and the integration-creator arm still admits a departed pod creator who created the connector. Without them, "refuse the creator" would pass by refusing every pod that names one.

Runs and lint

• __tests__/unit/routes — 140 suites / 1068 tests, green (this adds one suite and nine tests).
• The same tree with this file excluded — 3262 passed, 24 skipped, so nothing else depends on the old behaviour.
• routes/integrations.ts: 0 eslint errors and 0 warnings on any touched line — intersected eslint's line numbers with the diff's + ranges rather than comparing totals; no fatal: true anywhere in the run.
• Disclosed: the new test file carries the un-gated .js corpus's import/no-unresolved + import/extensions errors on its .ts requires, exactly like every other test file in that corpus. Fixing that corpus is its own task.

Gate: Vera.