feat(templates): upgrade A2A agents to SDK v1

[notgitika]

Summary

• migrate the Google ADK and LangGraph A2A templates to a2a-sdk v1 types and agent cards
• use the opt-in bedrock-agentcore[a2a-v1] dependency path introduced by feat(a2a): migrate runtime integration to a2a-sdk v1 bedrock-agentcore-sdk-python#591
• preserve the Strands template on its supported a2a-sdk 0.3 path and native StrandsA2AExecutor
• discover the v1 agent-card endpoint with a fallback for existing v0.3 agents
• add unit coverage for both CLI and web UI endpoint fallback paths

Release coordination

This PR depends on aws/bedrock-agentcore-sdk-python#591 and publication of bedrock-agentcore >= 1.19.0, which provides the a2a-v1 extra. Do not release a CLI version containing these Google ADK and LangGraph template changes until that SDK version is available on PyPI. The Strands template is not gated on that release and continues to use the currently published [a2a] / a2a-sdk 0.3 path.

Validation

• full unit suite: 5,983 passed
• focused A2A and asset snapshot suite: 139 passed
• TypeScript typecheck, ESLint, Prettier, secretlint, and pre-commit hooks pass
• asset snapshots regenerated after merging current main

Closes #1146

[github-actions]

Package Tarball

aws-agentcore-0.24.2.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-0.24.2.tgz

[agentcore-devx-automation]

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

[agentcore-cli-automation]

Templates now require bedrock-agentcore[a2a] >= 1.19.0, but the latest published version on PyPI is currently 1.18.1 (see https://pypi.org/project/bedrock-agentcore/#history). The PR description acknowledges this dependency on aws/bedrock-agentcore-sdk-python#591 and its subsequent release.

If this PR is merged before the SDK release lands on PyPI, agentcore create for the Google ADK / LangGraph / Strands A2A frameworks will produce projects that fail at uv sync / pip install time with "no matching distribution found." This is a hard release-coordination gate.

Options:

1. Hold this PR until bedrock-agentcore 1.19.x is published to PyPI, then merge.
2. Cut a coordinated CLI release only after the SDK release ships.
3. If a partial rollout is intentional, please document that in the PR body (e.g., "do not release CLI until X").

Otherwise the code changes themselves look correct — AgentInterface(url=..., protocol_binding=..., protocol_version=...) matches the a2a-sdk 1.x proto definition, the v0.3→v1 endpoint fallback in fetchA2AAgentCard and handleA2AAgentCard is sensible, and the new tests cover both branches of the fallback.

A couple of smaller items I'd like a second look at, but which I don't consider blockers:

• src/cli/operations/dev/web-ui/handlers/a2a-proxy.ts: the fallback here only triggers on HTTP 404, and there are no tests for it (no a2a-proxy.test.ts exists at all). Would be nice to add a small test in this PR while you're touching the file, mirroring the ones you added for fetchA2AAgentCard.
• src/cli/operations/dev/invoke-a2a.ts (lines 30-49): the return null; after the inner for (const path of ...) loop is unreachable — the inner loop either returns a card, returns null on a non-404 error, or continues past agent-card.json to agent.json, where a non-ok status now falls through the if (res.status === 404 && path === '/.well-known/agent-card.json') guard and returns null with the warn log. Not a bug, just dead code you can drop.

[agentcore-devx-automation]

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