console: correct the source status values in MaintainedObjectSourceStatus - #38604

Motivation

MaintainedObjectSourceStatus (console/src/platform/maintained-objects/queries.ts) documents the status and error fields that the hydration-aggregate feed delivers. That feed selects status, error from mz_source_statuses (buildHydrationAggregateQuery, filtered only by type not in ('subsource','progress')), and the two comments do not match what that relation can contain:

• failed is never reported. The storage Status enum (src/storage-client/src/client.rs) has no such variant, its FromStr rejects the string, and no writer emits it. #38585 corrected the catalog comments and docs accordingly.
• dropped is missing from the list, though the relation reports it and this query does not filter it out.
• error is populated only for stalled; no other status carries one.

Description

Comment-only change to the two JSDoc lines. No behaviour change.

Not included, for the Console team to decide

While checking this I found that failed is not only a stale comment — it is a first-class value in the Console's source/sink status handling, for a status the database cannot produce:

• ConnectorStatus (console/src/api/materialize/types.ts) includes "failed".
• connectorStatusToHealth (console/src/platform/connectors/utils.ts) maps it to unhealthy.
• sourceStatusToColor (console/src/platform/clusters/format.ts) gives it a colour.
• StatusPill renders it.
• SOURCE_STATUS_BUCKETS (console/src/platform/maintained-objects/filters.ts) exposes it as a user-facing filter option labelled "Failed", which can never match a source or sink.

I left that alone deliberately: removing a union member touches exhaustive switches and a visible filter list, which is a UI decision and needs a typecheck run I can't do from here. Worth a look — as far as I can tell no released version ever produced failed, so this is not version-skew tolerance. Note ConnectorStatus is used only for sources and sinks; privatelink/SSH connection statuses are a separate set that legitimately includes failed.

Also not touched: console/types/materialize.d.ts still carries the old comment text in four places. It is kysely-codegen output ("do not edit it manually") and will correct itself on the next yarn gen:types against a build containing #38585.

Verification

Comments only, no code paths touched.