feat(net)!: remove the deprecated broadcast finish and abort

[kixelated]

Problem

The line #4031 made close() the one way to end a broadcast and deprecated the finished-versus-aborted split, which never survives a hop (a broadcast has no FIN on the wire). The deprecated APIs still need removing on dev, and closed() still carries an Error cause nobody can act on.

Depends on #4031 reaching main and then dev. This branch merges quest/m1/broadcast-close/README into dev so the deprecations exist to remove; until #4031 lands and main merges into dev, the diff here includes the line's commits (#4047, #4126). Kept as a draft until then.

Approach

• moq-net: drop broadcast::Producer::finish, abort, Consumer::is_finished, and the finished/abort state they read. Consumer::closed(), Dynamic::closed(), and Dynamic::poll_closed now return ().
• moq-ffi / libmoq: drop MoqBroadcastProducer::finish and moq_publish_finish.
• Bindings: drop Python finish(), Swift finish(), Go Finish(); Dart regenerated.
• JS: drop broadcast.Producer.close(abort) / Consumer.close(abort); closed narrows to GetPromise<null>.
• Kotlin forced end (decision): Kotlin gets broadcast.end(), via a uniffi.toml rename of the generated close() (replacing the old exclude). Kotlin's close()/use {} is AutoCloseable and only releases the handle, which ends the broadcast once no dynamic() handle remains. Without finish(), a Kotlin app holding a dynamic() serving loop would have no way to end the broadcast short of cancelling that loop. A distinct name is the cheapest fix that keeps the Rust semantics; the quest's Plan records it.

Impact

• Rust moq-net (breaking): broadcast::Producer::{finish, abort} and broadcast::Consumer::is_finished removed; broadcast::Consumer::closed() and broadcast::Dynamic::{closed, poll_closed} return () instead of Error.
• moq-ffi (breaking): MoqBroadcastProducer.finish() removed from every binding. Kotlin gains MoqBroadcastProducer.end() (the forced end), since close() there is AutoCloseable.
• libmoq C ABI (breaking): moq_publish_finish removed; use moq_publish_close.
• Python BroadcastProducer.finish(), Swift BroadcastProducer.finish(), Go BroadcastProducer.Finish() removed.
• @moq/net (breaking): broadcast.Producer.close(abort) and broadcast.Consumer.close(abort) lose the parameter; closed is GetPromise<null>.
• moq-transcode: an idle rung whose source broadcast closes now aborts its output with Error::Dropped explicitly (it was always Dropped in practice).
• Wire: none.

Alternatives

• Kotlin with no forced end: document that every dynamic() handle must be closed too. Rejected: a serving loop blocked in requestedTrack() only returns once the broadcast ends, so the two wait on each other.
• End the broadcast when the FFI producer handle drops, in every binding: makes Kotlin's close() a forced end, but changes drop semantics for Python, Swift, Go, and Dart apps that keep serving through dynamic() after releasing the producer.
• Another Kotlin name (closeBroadcast(), shutdown()): end() is shortest and matches the docs' wording.

Testing

Rust nextest (4384 pass), JS, Python, Go, Dart, and Kotlin checks pass locally; Kotlin gains a test that end() ends a broadcast while a dynamic() handle is still open. Swift is uncompiled locally (Linux).

Follow-ups

• The remove child keeps quest(broadcast-close): Broadcast close #4031 a draft while this PR waits on quest(broadcast-close): Broadcast close #4031: the line's Quests list should drop this child (it lands on dev separately) so quest(broadcast-close): Broadcast close #4031 can be sized and merged. Delete quest/m1/broadcast-close/remove.md and its README entry here once that is sorted.
• Kotlin's end() is additive and could ship on main ahead of this removal.

(Written by Claude Opus 5.5)

🤖 Generated with Claude Code

[kixelated]

#4173 moves this quest out of the broadcast-close line to quest/m1/broadcast-remove.md (Required: the line), so #4031 can land on main first. When this PR merges its base, delete the quest at that new path and drop its entry from quest/m1/README.md.

(Written by Claude Opus 5.5)

[chatgpt-codex-connector]

Codex Review Summary

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-26T00:20:58.297380Z	2a53e53	Draft marked ready

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