Add CI coverage for memory integration tests.

[Hweinstock]

Problem

Memory integration tests exist but only run locally. There is no automated CI coverage for memory control plane operations, stream delivery, or the Strands session manager integration. Regressions can only be
caught by manual testing.

Acceptance Criteria

• Memory integration tests run automatically in CI
• Required infrastructure and credentials are available in the CI environment
• Flaky tests (e.g. LLM-dependent assertions) are stabilized or excluded from CI runs

[jariy17]

I have some tests already created: #276