Add determinism tests for verdict artifact generation and update SHA256 sums script

- Implemented comprehensive tests for verdict artifact generation to ensure deterministic outputs across various scenarios, including identical inputs, parallel execution, and change ordering.
- Created helper methods for generating sample verdict inputs and computing canonical hashes.
- Added tests to validate the stability of canonical hashes, proof spine ordering, and summary statistics.
- Introduced a new PowerShell script to update SHA256 sums for files, ensuring accurate hash generation and file integrity checks.

docs/api/exceptions.md

@@ -1,12 +1,42 @@
-# Exceptions API (stub)
+# Exceptions API
 
-> Status: BLOCKED — awaiting exception API contract (DOCS-EXC-25-003).
+Exceptions are time-bound, tenant-scoped, auditable objects that change policy outcomes without mutating upstream evidence. They are used for waivers, compensating controls, and scoped suppressions in a way that is replayable offline.
 
-## To be provided
-- OpenAPI spec path (once delivered)
-- Endpoint list, payloads, errors, idempotency semantics
-- Deterministic examples (request/response NDJSON) with hashes
+This document is the entry point for exception contracts. Concrete shapes live in the gateway and Console schemas listed below.
 
-## Determinism
-- When examples/spec arrive, hash into `docs/api/SHA256SUMS`.
-- Keep sample payloads under `docs/api/exceptions/samples/` (one file per case) with stable ordering/fields.
+## Core Concepts
+
+- **Exception object:** `{ exceptionId, tenantId, scope, vuln, effect, justification, owner, expiration, evidenceRefs, policyBinding, status }`
+- **Append-only history:** changes are recorded as transitions; revoke/expire supersedes instead of delete.
+- **Two-phase activation (recommended):** `draft → staged → active` to support simulation and controlled rollout.
+- **Effects:** examples include `suppress`, `defer`, `downgrade`, `requireControl` (exact effect catalog is policy-driven).
+
+## API Surfaces
+
+- **Console CRUD/workflow (gateway-proxied):** see `docs/api/console/exception-schema.md`
+- **Policy + Exceptions gateway contract:** `docs/api/gateway/policy-exceptions.md`
+- **Exception workflow events (SSE stream):** `docs/api/gateway/exception-events.md`
+
+## Security & Headers
+
+Common requirements across endpoints:
+
+- `Authorization: Bearer <token>` (or DPoP where configured)
+- `X-StellaOps-Tenant: <tenantId>` (required)
+
+Scopes vary by deployment, but typically follow:
+
+- Read: `exception:read`
+- Create/edit: `exception:write`
+- Approve/reject/revoke: `exception:approve`
+- Simulation endpoints: `policy:simulate` (plus `exception:read` when simulating with overrides)
+
+## Offline / Air-Gap
+
+- Imports/exports are file-based (NDJSON or JSON) with deterministic ordering and UTC timestamps.
+- Signed exports (DSSE) are supported when Attestor is enabled; when disabled, exports remain hash-addressed and reproducible.
+
+## Related Docs
+
+- Exception Governance migration guide: `docs/migration/exception-governance.md`
+- CLI usage guide: `docs/modules/cli/guides/exceptions.md`