`conformance_multitenant` workflow row is stale vs the workflow-event schema (missing `d` tag → 400)

[vsima]

Environment

• Relay: local build from block/buzz main (2026-07-24), buzz-relay.
• Test: crates/buzz-test-client/tests/conformance_multitenant.rs, module
  workflows::workflow_trigger_is_community_confined.
• Re-verified at 38bf642f (main, 2026-08-05): the relay still rejects with
  exactly this string
  (crates/buzz-relay/src/handlers/command_executor.rs:668) and the test's
  workflow builder is unchanged, so the row still fails at setup.

What happens

The test fails at setup, not at the isolation assertion:

thread 'workflows::workflow_trigger_is_community_confined' panicked at
crates/buzz-test-client/tests/conformance_multitenant.rs:1706:
POST /events to http://a.localhost:3100 returned HTTP 400 Bad Request:
{"error":"invalid: missing d tag (workflow_id)"}

The test tries to create a workflow event, but the relay rejects it as missing
a d tag (workflow_id). The workflow is never created, so the isolation
property it means to check (a workflow trigger is confined to its community) is
never exercised — this is a false red, not an isolation failure.

Why

Version skew: the relay's workflow-event validation now requires a d tag
(workflow_id), but the conformance test's workflow-creation helper doesn't add
one.

Fix

Update the test's workflow-event builder to include the d / workflow_id tag
matching the current relay schema, so the row exercises the community-confinement
assertion again. (The sibling row workflows::approval_token_is_community_confined
is already a pending_lane todo!() stub — separate work.)