Make the SSE stream an AutoCloseable Iterable bound to response close

[OmarAlJarrah]

Problem

The SSE surface is a bare Sequence, and the reader explicitly disclaims ownership of the response (ServerSentEventReader.kt:23). Partial consumption can strand the connection.

Proposed change

Expose SseStream : AutoCloseable, Iterable<ServerSentEvent> that closes the underlying response when the stream closes or is partially consumed (mirror the close-on-partial-consume invariant pagination enforces). Turn the current doc-warnings into enforced constrain-once / is-closed guards.

Acceptance

• Closing the stream closes the response
• Partial consumption doesn't leak
• Tests + apiDump

Dependencies

• Blocks Generate a per-endpoint SSE adapter mapping events to typed models #62 — per-endpoint SSE adapter

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Priority: medium · Effort: medium