Add property-based tests for SBOM/VEX document ordering and Unicode normalization determinism

- Implement `SbomVexOrderingDeterminismProperties` for testing component list and vulnerability metadata hash consistency.
- Create `UnicodeNormalizationDeterminismProperties` to validate NFC normalization and Unicode string handling.
- Add project file for `StellaOps.Testing.Determinism.Properties` with necessary dependencies.
- Introduce CI/CD template validation tests including YAML syntax checks and documentation content verification.
- Create validation script for CI/CD templates ensuring all required files and structures are present.

tests/cicd-templates/README.md

@@ -0,0 +1,79 @@
+# CI/CD Template Tests
+
+This directory contains validation tests for the StellaOps CI/CD signing templates.
+
+## Running Tests
+
+```bash
+# Run all validation tests
+./validate-templates.sh
+
+# Run with verbose output
+bash -x validate-templates.sh
+```
+
+## Test Coverage
+
+| Test Suite | Description |
+|------------|-------------|
+| File Existence | Verifies all template files exist |
+| YAML Syntax | Validates YAML syntax using yq |
+| Workflow Structure | Checks required fields in workflows |
+| Documentation | Validates documentation content |
+| Cross-Platform | Ensures consistent patterns across platforms |
+| actionlint | GitHub Actions specific linting |
+
+## Prerequisites
+
+For full test coverage, install:
+
+```bash
+# yq - YAML processor
+brew install yq  # macOS
+# or
+apt-get install yq  # Debian/Ubuntu
+
+# actionlint - GitHub Actions linter
+go install github.com/rhysd/actionlint/cmd/actionlint@latest
+# or
+brew install actionlint
+```
+
+## Templates Tested
+
+### GitHub Actions
+- `stellaops-sign.yml` - Reusable signing workflow
+- `stellaops-verify.yml` - Reusable verification workflow
+- Example workflows for containers, SBOMs, verdicts
+
+### GitLab CI
+- `.gitlab-ci-stellaops.yml` - Include-able templates
+- `example-pipeline.gitlab-ci.yml` - Full pipeline example
+
+### Gitea
+- `release-keyless-sign.yml` - Release signing
+- `deploy-keyless-verify.yml` - Deploy verification
+
+## Expected Output
+
+```
+========================================
+CI/CD Template Validation Tests
+Sprint: SPRINT_20251226_004_BE
+========================================
+
+Checking required tools
+✓ PASS: yq is installed
+✓ PASS: actionlint is installed
+
+Testing GitHub Actions templates exist
+✓ PASS: .github/workflows/examples/stellaops-sign.yml exists
+...
+
+Test Summary
+========================================
+Passed: 25
+Failed: 0
+
+All tests passed!
+```