fix channel dispatch durability and stream identity

[hamb1y]

Scope

Channel dispatch fixes

Issues Fixed

• Fixes Bug: WebSocket channel drops proactive messages when no subscribers are connected #4062: WebSocket normal outbound messages are persisted before subscriber checks, so disconnected clients can replay proactive messages.
• Fixes Bug: stream delta coalescing ignores _stream_id and can merge distinct streams #4063: ChannelManager stream-delta coalescing includes _stream_id in the stream key.
• Fixes Bug: pending mid-turn messages lose sender/channel/chat runtime context #4064: pending mid-turn injected messages preserve runtime channel, chat, sender, and workspace context.

Key Files

• nanobot/channels/manager.py
• nanobot/channels/websocket.py
• nanobot/agent/loop.py

Validation

• uv run pytest tests/channels/test_channel_manager_delta_coalescing.py -q