fix(bb-realtime): align local message envelopes with AWS runtime

[ikenyal]

Problem

Issue #, if available: Fixes #253

The local Realtime WebSocket server emitted published messages as { type, channel, payload }, while the AWS runtime emits { type, channel, data }. This made local development expose a different wire envelope to direct and native clients.

Changes

• Emit the AWS-compatible data key from both local publish paths.
• Update mock middleware delivery to read data.
• Add regression coverage for EventEmitter broadcasts and client-originated publishes.
• Remove the documented mock/AWS envelope difference in packages/bb-realtime/DESIGN.md.
• Add a patch changeset for @aws-blocks/bb-realtime.

Validation

• npm run build
• npm run lint
• npm run lint:deps
• npm test
• npm run test:e2e:local
• npm run build --workspace=@aws-blocks/bb-realtime && npm test --workspace=@aws-blocks/bb-realtime (72 tests)
• Deployed the comprehensive sandbox app: the Realtime suite passed (7/7). The complete sandbox suite could not finish because the separate test account lacks an SES-verified noreply@example.com sender and the Bedrock agent did not respond before its timeout; the stack was destroyed afterward.

Checklist

• PR description included
• Tests are changed or added
• Relevant documentation is changed or added (and PR referenced)

---

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[changeset-bot]

🦋 Changeset detected

Latest commit: d38790e

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

This PR includes changesets to release 1 package

Name	Type
@aws-blocks/bb-realtime	Patch

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[Simone319]

Thank you for making the fix.

One minor comment:
Shall we update the payload from the root here as well? So that we don't need multiple payload -> data translation which is easy to miss.

[ikenyal]

Thanks, that is a good point. I updated the local broadcast bus to emit { channel, data } directly from Realtime.publish() and updated ws-server to consume that shape, removing the intermediate payload to data translation.

I also updated the direct broadcast and reconnect regression tests. The client-originated WebSocket publish request remains { action, channel, payload } because it is a separate existing input protocol; emitted message envelopes remain { type, channel, data }.

Validated with:

• npm run build
• npm run lint
• npm run lint:deps
• npm test
• npm run test:e2e:local