Improve integration failure diagnostics in CI

[thymikee]

Summary

• add a shared integration test context that records step history and captures last successful snapshot
• include rich failure output (last snapshot context, target ref presence, recent step history)
• write failure artifacts under test/artifacts////
• migrate Android and iOS integration tests to the shared step runner
• upload test/artifacts/** in Android and iOS workflow artifacts

Reviewer follow-up fixes

• instantiate integration context inside each test to avoid cross-test state leakage
• fix iOS click step label to match the actual command (@e21)

[github-actions]

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