Add SessionManagement PowerShell module and lifecycle tests

[simond4680-sys]

Summary

• add a new PowerShell SessionManagement module with a class-based lifecycle runner
• implement four explicit phases: SessionHandshake, ActivationRecord, Cleanup, Verify
• add unit tests and integration tests for success and failure paths
• document module import, example usage, and test commands in README

Validation

• Invoke-Pester -Script .\powershell\SessionManagement\tests\SessionManager.Tests.ps1
• Invoke-Pester -Script .\powershell\SessionManagement\tests\SessionManager.Integration.Tests.ps1

Co-Authored-By: Oz oz-agent@warp.dev