Rusi transport emit subscription errors

[oncicaradupopovici]

Problem

When the rusi sidecar returns subscription-level stream errors (e.g. stan: subscribe request timeout), the gRPC channel remains READY so no connection-level error fires. The rusi transport only logged these errors and never forwarded them to the Subscription EventEmitter, causing subscribers to silently hang with no possibility of recovery.

Solution

Rewrite rusiSubscription to forward call stream errors and end events onto the subscription's EventEmitter, so callers (e.g. messaging-host) can react to subscription-level failures.

Changes

rusiSubscription(call, subject)

• Added named onError handler: logs the error and calls sub.emit('error', e)
• Added named onEnd handler: synthesises an Error and calls sub.emit('error', err) — a stream ending unexpectedly is treated as an error
• unsubscribe() removes both listeners via removeListener before calling call.cancel(), preventing spurious error events on intentional shutdown (same outcome as .NET's catch when StatusCode == Cancelled filter, without needing to inspect the error type)
• subject parameter added and threaded through from subscribe() for use in log messages

Tests: 4 new cases

• subscribe registers error and end listeners on call
• unsubscribe removes error and end listeners before cancelling
• subscription emits error when call emits error
• subscription emits error when call emits end

[changeset-bot]

🦋 Changeset detected

Latest commit: e3b6b70

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@totalsoft/message-bus	Patch

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[Copilot]

Pull request overview

Updates the Rusi transport subscription wrapper so subscription-level gRPC stream failures (error/end) are surfaced to consumers via the returned Subscription EventEmitter, instead of only being logged.

Changes:

• Forward gRPC call stream error events to the subscription (sub.emit('error', e)).
• Treat unexpected end of the stream as a subscription error and emit it to the subscription.
• Update unsubscribe logic to remove listeners before cancelling, and add tests for listener wiring and emitted errors.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
packages/message-bus/src/transport/rusi/index.ts	Reworks rusiSubscription to listen for call error/end and forward them to the returned subscription; updates unsubscribe teardown.
packages/message-bus/tests/transport/rusi.test.ts	Adds unit tests validating listener registration/removal and that error/end propagate to subscribers.

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