chore(release/v2-candidate): release 2.0.0-alpha.3

[Jacksunwei]

🤖 I have created a release beep boop

2.0.0-alpha.3 (2026-04-09)

Features

• Workflow Orchestration: Added Workflow(BaseNode) graph orchestration implementation, support for lazy scan deduplication and resume for dynamic nodes, partial resume for nested workflows, and state/artifact delta bundling onto yielded events.
• CLI and Web UI: Added support for Workflow graph visualization in web UI, improved graph readability with distinct icons and shapes, and active node rendering in event graph.
• Documentation: Added reference documentation for development (skills like adk-style, adk-git, and observability architecture).

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