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/governance/default-approval-protocol.md

@@ -58,7 +58,7 @@ When a decision is needed, create a **Decision Contract** document:
 After 48 hours without objection:
 1. Update `Status:` to `DEFAULT-APPROVED`
 2. Update dependent sprint files
-3. Log in `docs/governance/decisions-log.md`
+3. Record the decision in the relevant sprint file execution log (`docs/implplan/SPRINT_*.md`)
 
 ## Owner Manifest Pattern
 
@@ -103,5 +103,5 @@ If a decision is contested after default approval:
 
 ## References
 
-- [Approvals and Routing](./approvals-and-routing.md)
-- [Exceptions](./exceptions.md)
+- Exceptions API entry point: `docs/api/exceptions.md`
+- Exception governance migration guide: `docs/migration/exception-governance.md`