feat: Add ArtifactStreamer helper for streaming text artifact updates

[kevinlu310]

Description

Add ArtifactStreamer helper for streaming text artifact updates.

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Fixes #833 🦕

[gemini-code-assist]

Summary of Changes

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This pull request introduces a new utility class, ArtifactStreamer, designed to simplify the process of streaming text content into a single artifact over a series of events. This enhancement provides a structured way to handle incremental updates to artifacts, ensuring that all parts of a streamed artifact are correctly associated and finalized according to the A2A specification. It streamlines the creation and management of dynamic text artifacts.

Highlights

• New ArtifactStreamer Helper: Introduced the ArtifactStreamer class to facilitate streaming text content into a single artifact across multiple events, ensuring proper append semantics.
• Stable Artifact IDs: The ArtifactStreamer generates a stable artifact ID upon construction, allowing all streamed chunks to reference the same artifact consistently.
• Event Emission Methods: Provided append and finalize methods within ArtifactStreamer to emit TaskArtifactUpdateEvent objects for incremental text updates and to signal the completion of the artifact stream, respectively.

Changelog

• src/a2a/utils/init.py
  • Imported ArtifactStreamer from a2a.utils.artifact.
  • Added ArtifactStreamer to the __all__ export list.
• src/a2a/utils/artifact.py
  • Imported TaskArtifactUpdateEvent from a2a.types.
  • Implemented the ArtifactStreamer class, including its __init__, append, and finalize methods for managing text artifact streaming.
• tests/utils/test_artifact.py
  • Imported ArtifactStreamer and TaskArtifactUpdateEvent for testing purposes.
  • Added a new test class TestArtifactStreamer with comprehensive unit tests covering artifact ID generation, naming, append logic, and finalization.

Activity

• The pull request was opened by kevinlu310.
• The PR description includes a checklist for contributing, conventional commit guidelines, and mentions fixing issue [Feat]: Add streaming-aware helper for artifact updates #833.
• No specific review comments or progress updates are available in the provided context.

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Code Review

This pull request introduces a helpful ArtifactStreamer class for managing streaming text artifact updates, which is a great addition. The implementation is clean and comes with a comprehensive set of unit tests. My feedback focuses on a minor improvement to enhance encapsulation by making internal attributes private, which is a common best practice in Python for clearer API boundaries. I've provided a set of related suggestions to apply this change consistently across the new class and its tests.