0653 — Consumer names the public group handle

Supersedes the affected naming clauses of [0644] and [0646].

Context

[0646] nested the consuming handle under its typed topic but changed its name from Consumer to Group. That nesting requires a generic handle; it does not require the Group name. Go permits a Consumer method beside a Consumer type, and pkg/consume.Consumer does not collide with pkg/consumer.Consumer because the declarations live in separate packages.

Consumer group remains the domain noun for the durable row, SQL tables, diagnostics, metrics scopes, and operator commands. On the Go facade, however, the caller selects the consumer that will register and run, so Group makes the call tree switch nouns at its most common step.

Decision

The typed topic handle names a consumer with Topic[Message](name).Consumer(groupName) *ConsumerHandle[Message] and lists the materialized values with Consumers(ctx) ([]*Consumer, error). The consumer’s nested observability handles are ConsumerMetricsHandle and ConsumerAlertsHandle.

The materialized value is declared as consume.Consumer so vulkan’s alias keeps the declaration’s name. Controller verbs, datastore rows, table and column names, errors, owner kinds, metrics types, log attributes, CLI commands, and prose continue to say consumer group where they describe that mechanism.

Consequences

The Go rename is compile-time breaking and JSON is unchanged. There is no compatibility alias: pre-v1 callers update Group to Consumer and Groups to Consumers. The topic still owns the message type, and every verb continues to resolve the same consumer-group rows through the same controller path.