FCE-3224: Fix reconnect race condition

[MiloszFilimowski]

Description

• ConnectionManager: stop excess recvonly transceivers (preferring orphaned mid === null) before adding new ones, and exclude already-stopped transceivers from counting and stop-candidate selection so server-track counts stay in sync after reconnects.
• webRTCEndpoint: serialize all incoming media events (including connected) through a single promise-chain queue with one handleMediaEvent entry point, so async handlers run strictly in order; dedup the duplicate local endpoint metadata parse/set in handleConnected.
• Tests: await receiveMediaEvent in event/method tests; add serializedMediaEvents.test.ts (offer/answer ordering, pre-connect events are dropped, consecutive connected events stay in order) and addTransceiversIfNeeded.test.ts (clamping, negative-delta regression, stopped-transceiver counting and stop-candidate exclusion).

Motivation and Context

Fixes reconnect-related state drift where stale recvonly transceivers accumulated and async server events interleaved, leaving the client and server out of sync.

Documentation impact

• Documentation update required
• Documentation updated in another PR
• No documentation update required

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to
  not work as expected)

[linear]

FCE-3224 Fix reconnect race condition

[Copilot]

Pull request overview

Fixes reconnect-related state inconsistencies in webrtc-client by keeping transceiver counts aligned with server track counts and ensuring async media-event handlers execute in-order.

Changes:

• Stop excess recvonly transceivers (preferring orphaned mid === null) before adding new ones in ConnectionManager.
• Serialize non-connected media events in WebRTCEndpoint via a promise queue; refactor connected handling into handleConnected.
• Update/add tests to await receiveMediaEvent, plus new coverage for transceiver clamping/stopping and media-event ordering.

Reviewed changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
packages/webrtc-client/src/webRTCEndpoint.ts	Adds a media-event promise queue and refactors connected handling.
packages/webrtc-client/src/ConnectionManager.ts	Adds logic to stop excess recvonly transceivers and clamps deltas.
packages/webrtc-client/tests/utils.ts	Makes setupRoom async and awaits media-event processing for deterministic tests.
packages/webrtc-client/tests/events/vadNotificationEvent.test.ts	Awaits media events; replaces done patterns with awaited promises.
packages/webrtc-client/tests/events/trackUpdatedEvent.test.ts	Awaits media events and modernizes async assertions.
packages/webrtc-client/tests/events/trackRemovedEvent.test.ts	Awaits media events and makes event assertions deterministic.
packages/webrtc-client/tests/events/trackAddedEvent.test.ts	Awaits media events and makes event assertions deterministic.
packages/webrtc-client/tests/events/endpointUpdatedEvent.test.ts	Awaits media events in metadata update paths.
packages/webrtc-client/tests/events/endpointRemovedEvent.test.ts	Awaits media events; modernizes rejection assertions and event checks.
packages/webrtc-client/tests/events/endpointAddedEvent.test.ts	Awaits media events for state updates.
packages/webrtc-client/tests/events/encodingSwitchedEvent.test.ts	Awaits media events and modernizes async assertions.
packages/webrtc-client/tests/events/serializedMediaEvents.test.ts	New test ensuring queued media events preserve ordering across async handlers.
packages/webrtc-client/tests/addTransceiversIfNeeded.test.ts	New unit tests for add/stop behavior and negative-delta regression coverage.

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