Automate currently manual high-risk test suites before beta

[adolago]

Problem

Several high-risk suites are manual/ignored and not gating in CI: WinRM integration, real SSH integration, HPC scale validation, and fuzz/property-style callback stress tests.

Why this blocks beta

High-risk runtime paths can regress without automated detection before release.

Evidence

• tests/winrm_integration_tests.rs:55
• tests/real_ssh_tests.rs:1
• tests/hpc_scale_validation_tests.rs:1
• tests/callback_fuzz_tests.rs:14

Acceptance criteria

• Introduce scheduled or pre-release automated jobs for these suites.
• Define pass/fail ownership and triage policy for flaky external-environment suites.
• Add minimal smoke coverage for each suite on CI-managed infrastructure.
• Document which suites are required for beta release sign-off.

[adolago]

Dependency: blocks #790 (beta entry criteria umbrella).