fix(sdk-swift): queue outbound messages during RelayObserver reconnect

[miyaontherelay]

Summary

Address follow-up review feedback from #627.

When _handleSocketError is entered from the receive-error path, isConnectionReady could remain true during the reconnect delay. That allowed sendChannel / sendDirect to write to a broken socket instead of queueing outbound messages for replay after reconnect.

Fix

• set isConnectionReady = false at the start of _handleSocketError

Why it matters

This ensures outbound messages are queued in pendingOutbound while the observer is reconnecting, instead of being silently dropped.

Follow-up to

• feat(sdk-swift): add RelayObserver proxy client for UI consumers #627
• Devin review feedback on feat(sdk-swift): add RelayObserver proxy client for UI consumers #627

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[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

View in Devin Review to see 2 additional findings.