claudetool: redact initial commit hash in test fixtures
This was causing failures when switching between Go versions,
because the go version ends up in the go.mod, which changes
the git hash.
diff --git a/claudetool/testdata/vet_error_test.txtar b/claudetool/testdata/vet_error_test.txtar
index 0163a81..6f2c7c7 100644
--- a/claudetool/testdata/vet_error_test.txtar
+++ b/claudetool/testdata/vet_error_test.txtar
@@ -23,7 +23,7 @@
-- .run_test --
# Errors
-Test regressions detected between initial commit (656e4d573cb77a30ebce29ebb974533ece282946) and HEAD:
+Test regressions detected between initial commit (INITIAL_COMMIT_HASH) and HEAD:
1: sketch.dev: Previously had no tests, now has build/vet errors