ci: configure and stabilize CI/CD pipeline

- fix runner configuration issues
- correct workflow labels and execution environment
- resolve dependency issues in pipeline (python deps)
- improve reliability of automation runs

migration-validation-framework/scenarios/before_after_comparison.md

@@ -0,0 +1,19 @@
+# Scenario: Before/After Migration Comparison
+
+## Description
+
+Compare a pre-cutover host snapshot against a post-cutover snapshot and determine whether the migrated system is ready for production traffic.
+
+## Commands
+
+```bash
+cd migration-validation-framework
+python3 cli.py compare examples/before.json examples/after.json --output /tmp/migration-diff.json
+```
+
+## Expected Result
+
+- The command writes a JSON diff.
+- The result is `FAIL` because `sshd` is failed after migration.
+- The risk assessment highlights the `/var` disk usage increase.
+- The remediation path is to restore SSH and reduce or expand `/var` before approving cutover.