test: add unit tests for message bus

[Tonyfudecai]

Description

Add unit tests for the message bus component to ensure reliable message routing.

Requirements

• Test publish/subscribe
• Test multiple subscribers
• Test message filtering
• Achieve >80% coverage for bus package

Skills

Go, testing

[keysmastersyabro]

Hi, I'm Fadi (@keysmastersyabro). Would you fund US$30 for a focused fix and tests for the message bus, related to #4?

I inspected 5936a44 and reproduced a shutdown defect: after Close and draining queued messages, both consumer methods return a zero-value message with true. A minimal local patch propagates the receive status. Six tests pass with the race detector and 100% bus-package statement coverage, covering round trips, cancellation, concurrent consumers, channel-keyed handlers and shutdown.

The existing API is a shared queue, not broadcast subscriptions, and has no predicate filters. Please clarify whether #4 requires those new APIs or tests of existing semantics. I use AI-assisted development and will disclose exact validation in the PR.

Please confirm the paid scope, reward, and payout method/timing before treating this as an assigned bounty. There is no payment obligation from this proposal alone.