Tighten the Hands brief: defined mutations, base-commit proofs, started scripts

The rules come from the first Eureka pipeline-state cuts. Soul could not rerun
mutations that were only named. A digest captured from new code proved nothing
about the old code. A detached mutation script died silently on a parse error.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

references/briefs.md

@@ -74,7 +74,12 @@ Standing rulings: <short list>.
 
 Every rule the spec or the operator names gets a test that fails under its own
 mutation. Run the mutations against the final spelling of the code and restore
-afterwards.
+afterwards. In the report, define each mutation exactly (what line changed and
+how) so Soul can rerun it; a mutation named only "C3" cannot be checked.
+When a claim is "behaviour unchanged", a value captured from the new code is not
+evidence. Pin it with a value computed at the base commit.
+Detached scripts: confirm the log starts within 60 s; a script that dies on a
+parse error is silent otherwise.
 
 Commits:
 - Small and pushed.

references/changelog.md

@@ -2,6 +2,16 @@
 
 Record each change to the skill together with the evidence that motivated it.
 
+## 2026-09-15: Hands brief rules from the Eureka pipeline-state campaign
+
+- **Define every mutation in the report.** Soul could not rerun Hands' Cut 2
+  mutations "C1-C5" because the report named them without saying what changed.
+- **"Unchanged" is proven against the base commit.** Cut 2 pinned a Mind
+  receipt digest captured from the new code. Soul had to rerun the test at the
+  base commit to show it matched.
+- **Check that a detached script started.** A Cut 1 mutation script died on a
+  PowerShell parse error, and its monitor sat silent for 30 minutes.
+
 ## 2026-09-15: renamed to Eureka; postmortem rules folded in
 
 - **Rename.** The operator named the skill-and-MCP form of the pipeline