server: own WebRTC offer cleanup

[yisding]

Problem

Each accepted WebRTC offer started a long-lived peer-close cleanup worker with raw asyncio.create_task() and tracked it in a manual set. The set supplied a strong reference, but duplicated lifecycle bookkeeping and left the worker outside the named runtime ownership model.

Changes

• create per-offer cleanup workers through a dedicated RuntimeTaskScope
• retain the task-to-session-key index needed for forced shutdown finalization
• start cleanup through one helper used by production and the force-escalation regression test
• release an empty standalone cleanup scope after server-stop cancellation settles
• reduce the reviewed raw-task-spawn inventory from 35 to 34
• document the per-offer cleanup owner in the WebRTC architecture guide

Why / impact

Every accepted peer now has an explicitly named, strongly owned cleanup task that remains discoverable until it releases the Session and capacity reservation. Existing cancellation and force-escalation semantics are preserved.

Root cause

The WebRTC routes' cleanup ledger was implemented before the shared runtime task-scope abstraction and had not yet been migrated in WS2.5.

Checks

• focused cleanup ownership and source-inventory tests — 10 passed
• broader WebRTC routes/capacity/source slice — 70 passed / 24 skipped
• Ruff on changed Python files — passed
• mypy on webrtc_routes.py — passed
• pre-commit hooks — passed

[coderabbitai]

Important

Review skipped

Auto reviews are disabled on base/target branches other than the default branch.

Please check the settings in the CodeRabbit UI or the .coderabbit.yaml file in this repository. To trigger a single review, invoke the @coderabbitai review command.

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro Plus

Run ID: 5ae58457-0ab6-4ffa-8539-ac2fc051076a

You can disable this status message by setting the reviews.review_status to false in the CodeRabbit configuration file.

Use the checkbox below for a quick retry:

• 🔍 Trigger review

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}