[codex] Draft sbom-diff-and-risk v0.8.0 release notes

Docs-only draft v0.8.0 release notes for policy decision explainability. No runtime, workflow, package metadata, tag, release, or publishing changes.

Author: stacknil

tools/sbom-diff-and-risk/RELEASE_NOTES_v0.8.0.md

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+# sbom-diff-and-risk v0.8.0
+
+`v0.8.0` is the policy decision explainability release.
+
+## Theme
+
+Policy decision explainability for machine-readable JSON reports.
+
+`v0.8.0` focuses on making local policy outcomes easier to inspect from JSON
+reports and reviewer documentation. It keeps the dependency diff model,
+existing CLI flags, Markdown output behavior, SARIF output behavior, workflows,
+release tags, and publishing status unchanged.
+
+This file is a draft release note. Drafting this file does not bump the package
+version, create a tag, create a GitHub Release, publish to TestPyPI, or publish
+to production PyPI.
+
+## Highlights
+
+- Added stable policy decision explanation fields to JSON policy findings.
+- Documented those fields in
+  [docs/report-schema.md](docs/report-schema.md).
+- Added reviewer-facing interpretation guidance in
+  [docs/policy-decision-explainability.md](docs/policy-decision-explainability.md).
+- Kept `summary.policy` unchanged as the compact policy count/status surface.
+- Kept production PyPI intentionally deferred.
+
+## Machine-readable policy explainability
+
+Policy findings in JSON reports can now include additive explanation fields:
+
+- `decision_reason`
+- `policy_rule`
+- `severity_source`
+- `matched_threshold`
+- `observed_value`
+
+These fields explain why a local policy rule produced a block, warning, or
+suppression. They are policy-decision metadata only; they are not dependency
+safety verdicts, CVE results, or proof that a package is safe or unsafe.
+
+The fields appear only on policy finding objects, such as:
+
+- `policy_evaluation.blocking_violations`
+- `policy_evaluation.warning_violations`
+- `policy_evaluation.suppressed_violations`
+- `blocking_findings`
+- `warning_findings`
+- `suppressed_findings`
+- provenance policy impact sections
+
+Risk findings in `risks` remain local heuristic findings. They do not receive
+policy-decision metadata unless policy evaluation maps them into policy
+findings.
+
+## JSON schema / compatibility notes
+
+- The JSON report schema remains conservative and additive where possible.
+- Existing `summary.policy` behavior is unchanged.
+- Existing `--out-json` behavior remains the full JSON report output.
+- Existing `--summary-json PATH` behavior remains summary-only output.
+- Existing policy pass, warn, and fail behavior is unchanged.
+- Existing CLI flags are unchanged.
+- Consumers should treat unrecognized future fields as additive report data.
+
+## Documentation and evidence surfaces
+
+- JSON report schema:
+  [docs/report-schema.md](docs/report-schema.md)
+- Policy schema:
+  [docs/policy-schema.md](docs/policy-schema.md)
+- Policy decision explainability:
+  [docs/policy-decision-explainability.md](docs/policy-decision-explainability.md)
+- Reviewer evidence pack:
+  [docs/reviewer-evidence-pack.md](docs/reviewer-evidence-pack.md)
+- GitHub Actions consumer example:
+  [docs/github-actions-consumer-example.md](docs/github-actions-consumer-example.md)
+- Production PyPI decision gate:
+  [docs/pypi-production-publishing-decision.md](docs/pypi-production-publishing-decision.md)
+
+The v0.8 documentation keeps the release/distribution evidence surfaces
+separate from tool behavior. GitHub workflow artifact attestations, GitHub
+Release asset verification, TestPyPI Trusted Publishing validation, and future
+production PyPI Trusted Publishing provenance answer different trust questions.
+
+## Distribution status
+
+- The latest published GitHub Release remains `v0.7.0` until `v0.8.0` is
+  intentionally tagged and released.
+- This draft does not publish to TestPyPI.
+- This draft does not publish to production PyPI.
+- Production PyPI publishing remains intentionally deferred.
+- No production PyPI workflow is added.
+
+## Not in this release
+
+- No new CLI flags.
+- No Markdown output behavior changes.
+- No SARIF output behavior changes.
+- No workflow changes.
+- No package version bump in this draft PR.
+- No tag or GitHub Release in this draft PR.
+- No PyPI/TestPyPI publishing.
+- No production PyPI workflow.
+- No hidden network behavior.
+- No CVE lookup or CVE resolution.
+- No dependency safety verdicts.