Add completion-aware realtime attachment and session-scoped detach

[copyberry]

Add completion-aware realtime attachment and session-scoped detach

Why

A delayed detach or cleanup from an older realtime conversation must not close its replacement or end the replacement's history segment. Realtime start parameters can also contain credentials in text and transport endpoints, so diagnostics should avoid exposing them.

What changed

• Add RealtimeConversationAttach to report the connection attempt's result through a reply channel, using the sequential start path.
• Add RealtimeConversationDetach to close only the matching realtime_session_id after earlier starts finish. Detaching an older session leaves the replacement connected.
• Emit the previous conversation's close event before starting its replacement, and prevent stale fanout cleanup from closing or clearing the replacement's context.
• Limit ConversationStartParams debug output to output modality, initial item count, and protocol version.

Testing

Add coverage for attachment completion after the handshake, stale detaches, failed replacement and retry, natural-close ordering, handoff history after replacement, and debug redaction for existing-call and WebRTC transports.

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	🔄 Running since 2026-10-07T01:29:12.241799Z	a87b40e	PR opened

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