Add tests for SBOM generation determinism across multiple formats

- Created `StellaOps.TestKit.Tests` project for unit tests related to determinism.
- Implemented `DeterminismManifestTests` to validate deterministic output for canonical bytes and strings, file read/write operations, and error handling for invalid schema versions.
- Added `SbomDeterminismTests` to ensure identical inputs produce consistent SBOMs across SPDX 3.0.1 and CycloneDX 1.6/1.7 formats, including parallel execution tests.
- Updated project references in `StellaOps.Integration.Determinism` to include the new determinism testing library.

docs2/release/release-notes.md

@@ -0,0 +1,22 @@
+# Release notes and templates
+
+Release notes
+- Historical release notes live under docs/releases/.
+- Use release notes for time-specific changes; refer to docs2 for current behavior.
+
+Determinism snippet template
+- Use a deterministic score summary in release notes when publishing scans.
+
+Template
+```
+- Determinism score: {{overall_score}} (threshold {{overall_min}})
+  - {{image_digest}} score {{score}} ({{identical}}/{{runs}} identical)
+- Inputs: policy {{policy_sha}}, feeds {{feeds_sha}}, scanner {{scanner_sha}}, platform {{platform}}
+- Evidence: determinism.json and artifact hashes (DSSE signed, offline ready)
+- Actions: rerun stella detscore run --bundle determinism.json if score < threshold
+```
+
+Related references
+- release/release-engineering.md
+- operations/replay-and-determinism.md
+- docs/release/templates/determinism-score.md