fix(moq-lite): exit run_send_bandwidth when the session closes

[kixelated]

Summary

• run_send_bandwidth (introduced in Add bandwidth estimation for adaptive bitrate control #1208) spawns a detached task that clones the underlying web_transport_trait::Session, but its select! arms only wait on producer.closed() / producer.used() / producer.unused(). None of those fire when the wrapping moq_lite::Session drops — the task is the sole Producer, so producer.closed() can never transition, and the outer loop's producer.used() sits forever waiting for a new consumer on a dead session.
• Net effect: every accepted quinn-backed session leaks a task that permanently pins the cloned session, the underlying quinn::Connection, and its StreamsState (HashMaps sized to max_concurrent_*_streams). On moq-relay with DEFAULT_MAX_STREAMS = 10_000, that's ~1.5–3 MB of live heap per connection accumulating unboundedly.
• Confirmed via jemalloc heap profiles on use.cdn.moq.dev: ~484 MB retained after 53 min / 328 accepted connections, 79% of it in quinn_proto::endpoint::Endpoint::accept → hashbrown::HashMap::insert → RawTable::reserve_rehash inside StreamsState::new.

Fix

Wrap the existing polling logic in an outer select! that also listens on session.closed(), so the task exits as soon as the transport dies. Extract the polling loop into run_send_bandwidth_inner so all termination conditions live in one place.

Bumps moq-lite to 0.15.11.

Test plan

• just check passes locally
• Deploy to a single relay node and watch RSS over several hours
• Confirm with a follow-up heap dump that quinn_proto::Connection::new is no longer dominant

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ℹ️ Recent review info

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Configuration used: Organization UI

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Run ID: 25166fad-24b5-459e-a6c5-9f301c58aaea

📥 Commits

Reviewing files that changed from the base of the PR and between 8bf9923 and 271ea0f.

⛔ Files ignored due to path filters (1)

• Cargo.lock is excluded by !**/*.lock

📒 Files selected for processing (2)

• rs/moq-lite/Cargo.toml
• rs/moq-lite/src/session.rs

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Walkthrough

The pull request includes a patch version increment for the moq-lite crate and refactors the run_send_bandwidth function in src/session.rs. The refactoring introduces an outer tokio::select! construct that races the session closure, producer closure, and polling logic. The previous loop logic is extracted into a new run_send_bandwidth_inner function, and in-loop selection branches for producer closure monitoring are removed in favor of error handling from the used() call within the inner loop.

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately describes the main fix—exiting run_send_bandwidth when the session closes—which is the core change across all modified files.
Description check	✅ Passed	The description comprehensively explains the memory leak issue, root cause, the implemented fix, and test plan; all directly related to the changeset.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

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✨ Finishing Touches

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🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/send-bandwidth-leak

✨ Simplify code

• Create PR with simplified code
• Commit simplified code in branch fix/send-bandwidth-leak

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