Closing any subscriber set the shared `recv_ready` event, even when
another receiver owned the source read. Waiting peers then looped
until an idle source produced another value.
Give each receiver private source-read and peer-wait cancellation
scopes. Closing a waiting peer interrupts only that peer. Closing
the source owner discards post-close source outcomes and then wakes
peers for a clean ownership handoff.
Keep outer task cancellation as `trio.Cancelled`; only explicit
receiver close maps either private scope's cancellation to
`ClosedResourceError`. Assert that scope cancellation implies the
receiver is closed and document the source-owner key check.
Prompt-IO: ai/prompt-io/opencode/20260812T150027Z_c2a6ccef_prompt_io.md
(this patch was generated in some part by `opencode` using `gpt-5.6-sol` (`openai`))
Gud Boi