feat(templates): upgrade A2A agents to SDK v1

[notgitika]

Summary

• migrate Google ADK, LangGraph, and Strands A2A templates to a2a-sdk v1 types and agent cards
• replace the Strands 0.3-only executor adapter with a small v1 AgentExecutor implementation
• discover the v1 agent-card endpoint with a fallback for existing v0.3 agents
• require bedrock-agentcore[a2a]>=1.19.0, which will contain the coordinated runtime migration

Depends on aws/bedrock-agentcore-sdk-python#591 and publication of the SDK release containing it. Existing v0.3 outbound CLI invocation remains unchanged and is handled by the SDK compatibility route.

Validation

• full unit suite: 5,976 passed
• TypeScript typecheck, ESLint, Prettier, secretlint, and build pass
• generated Google ADK, LangGraph, and Strands projects through the built CLI
• resolved each generated project with a2a-sdk 1.1.2 and the local SDK change
• compiled each generated main.py and imported its framework/A2A v1 APIs

Closes #1146

[github-actions]

Package Tarball

aws-agentcore-0.24.1.tgz

How to install

gh release download pr-1810-tarball --repo aws/agentcore-cli --pattern "*.tgz" --dir /tmp/pr-tarball
npm install -g /tmp/pr-tarball/aws-agentcore-0.24.1.tgz

[agentcore-devx-automation]

Claude Security Review: no high-confidence findings. (run)