refactor: introduced ChannelState enum for explicit channel closure handling

[yug49]

Resolves #222

Description

This PR addresses the issue of ambiguous channel closure handling by introducing a ChannelState enum with explicit Open and Closed variants that makes the code intent clear:

pub enum ChannelState {
    /// The channel is open and the message was successfully sent.
    Open,
    /// The channel is closed (receiver dropped), no further messages can be sent.
    Closed,
}

Before vs After

Before:

if !sender.try_stream(Notification::ReorgDetected).await {
    return; // Channel closed
}

After:

if sender.try_stream(Notification::ReorgDetected).await.is_closed() {
    return;
}

Testing

• Added comprehensive tests for ChannelState enum
• Added tests for TryStream trait behavior with open/closed channels

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[0xNeshi]

Hi @yug49 thanks for contributing another PR!
As mentioned in the other PR, there may be a delay before we can thoroughly review your PRs.
Thank you once again!

[yug49]

Sure, no problem