Merge root message entities in Activity

[heyitsaamir]

Summary

• Make Activity.addEntity/addEntities merge root schema.org Message entities instead of blindly appending them
• Keep AI-generated labels and citations on one root message entity
• Add regression coverage in the Activity tests

Why this matters

• This shows up when a message is assembled in pieces, like streaming a response or combining multiple helpers that each add root Message metadata
• Before this change, those pieces could leave you with multiple root Message entities on the same activity, which Teams doesn’t love
• In practice that means features like AI-generated markers and citations could get split across duplicate root entities

Test plan

• cd packages/api && npx jest --runInBand src/activities/activity.spec.ts
• cd packages/apps && npx jest --runInBand src/http/http-stream.spec.ts

[Copilot]

Pull request overview

This PR updates Activity entity handling so that multiple root schema.org Message entities are merged into a single root message entity, ensuring properties like AI-generated labels (additionalType) and citations are consolidated rather than duplicated across multiple root entities.

Changes:

• Updated Activity.addEntity() to detect root https://schema.org/Message entities and merge them into the existing root message entity instead of appending.
• Updated Activity.addEntities() to route through addEntity() so the same merge behavior applies to batch additions.
• Added a regression test covering merge behavior when adding multiple root message entities alongside other entity types.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
packages/api/src/activities/activity.ts	Implements root message entity detection + merge logic, and updates addEntities() to reuse addEntity() semantics.
packages/api/src/activities/activity.spec.ts	Adds regression coverage to ensure multiple root message entities are merged into one and retain key properties.

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[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

[heyitsaamir]

Good point. We should use the claim.position here to do the dedupe. Take the newest one.

[Copilot]

Updated in 7a672df: citations are now deduplicated by Claim.position during root message entity merge, with later entries taking precedence.