Expose connectionStateStream in pipe_client

[Komoszek]

No description provided.

[Copilot]

Pull request overview

This PR adds support for exposing connection state changes as a Stream in the PipeClient by implementing a state change stream in the underlying HubConnection class.

Key Changes:

• Added a StreamController to HubConnection to track and broadcast connection state changes
• Introduced an updateConnectionState method that updates both the internal state and emits to the stream
• Exposed the connection state stream through both HubConnection and PipeClient public APIs

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 5 comments.

File	Description
dart/lib/signalr_core/src/hub_connection.dart	Implements connection state streaming by adding a StreamController, replacing direct state assignments with updateConnectionState calls, and exposing the stream via a public getter
dart/lib/leancode_pipe/pipe_client.dart	Exposes the connection state stream by mapping HubConnection states to PipeConnectionStates and providing a public getter

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[mateusz-pietras]

LGTM