Baseline shared build caches by path list, not counts

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

references/briefs.md

@@ -80,6 +80,9 @@ 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.
+Shared build caches: record a full path list before building, not only counts,
+and delete exactly the new paths afterwards. Counts cannot attribute hardlinked
+or rewritten outputs.
 
 Commits:
 - Small and pushed.

references/changelog.md

@@ -9,6 +9,9 @@ Record each change to the skill together with the evidence that motivated it.
 - **"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.
+- **Baseline shared build caches by path list.** A Cut 2 Soul pass left about
+  401 MB in the shared cargo target that it could not attribute. It had
+  recorded only counts, so it did not delete blind.
 - **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.