feat(ci): add prompt and managed agent cloud e2e pipeline

[Zhijie Huang (hund030)]

Summary

Add public-repo cloud E2E coverage for azd prompt and managed agents alongside hosted-agent validation. The pipeline selects changed samples on PRs and supports scheduled and manual full runs; it requires separate Azure DevOps registration and resource authorization.

Changes

• .azure-pipelines/prompt-agents-samples-ci.yml: discover, deploy, invoke, assert, recover, and summarize prompt/managed samples, with SKIP_PROVISION controlling warm-resource reuse or disposable provisioning.
• prompt-agents scripts and contracts: validate sample capabilities, track owned resources, and fail closed on missing evidence or unverified cleanup.
• Shared fixture tooling and docs: resolve public prompt-agent contracts without changing hosted-agent defaults; add credential-free regression coverage and activation guidance.

Manual Validation

• Ran disposable 01-basic provisioning in westus2 against a test subscription.
• Ran the complete local prompt test suite with Git Bash and jq: 74 tests passed. A full live E2E pass and Azure DevOps pipeline registration/PR triggering remain unverified.

[azure-pipelines]

Azure Pipelines:
There may be pipelines that require an authorized user to comment /azp run to run.