volt: CHECK leg 4 reads HEAD's archive, not the worktree (Q142)

Leg 4 built its copy from the worktree, so a dirty tree broke the leg that
exists to prove a copy grades itself. It now extracts wizard-work/quill from
HEAD with git archive; legs 2 and 3 remain the worktree readings, and the
script sets pipefail so a failed archive cannot read as an empty tarball.

CHECK-quill-draft-compliance

@@ -12,6 +12,7 @@
 #
 # Exit codes: 0 all legs passed, 1 a leg failed, 2 a leg could not be graded.
 set -u
+set -o pipefail
 
 cd "$(dirname "${BASH_SOURCE[0]}")" || exit 2
 ROOT="$(pwd)"
@@ -60,32 +61,40 @@ else
     failed=$((failed + 1))
 fi
 
-# --- leg 4: a copy grades the copy, not this tree ----------------------------
+# --- leg 4: the COMMITTED artifact grades a copy of itself -------------------
+# The copy comes from HEAD (git archive), not from the worktree, so this leg is a
+# reading of the committed bytes and is unaffected by an uncommitted edit that
+# legs 2 and 3 already fault.
 mkdir -p "$WORK/lane" || exit 2
-cp "$LANE"/*.md "$LANE"/draft-compliance-report-2026-10-31.tsv \
+if ! git -C "$ROOT" archive HEAD wizard-work/quill 2>"$WORK/archive.err" \
-   "$LANE"/draft_compliance_rule.py "$LANE/draft_compliance_report.py" \
+     | tar -x -C "$WORK/lane" 2>>"$WORK/archive.err"; then
-   "$LANE/verify_draft_compliance.py" "$WORK/lane/" 2>/dev/null
+    row copy-parity "FAULT cannot archive HEAD"
-if python3 "$WORK/lane/verify_draft_compliance.py" >"$WORK/copy-clean.out" 2>&1; then
+    cat "$WORK/archive.err"
-    clean_rc=0
-else
-    clean_rc=$?
-fi
-# move one row's line count in the COPY's TSV: the copy must notice
-awk -F'\t' 'BEGIN{OFS="\t"} NR==3{$2=$2+1} {print}' \
-    "$WORK/lane/draft-compliance-report-2026-10-31.tsv" >"$WORK/mut.tsv" \
-    && mv "$WORK/mut.tsv" "$WORK/lane/draft-compliance-report-2026-10-31.tsv"
-if python3 "$WORK/lane/verify_draft_compliance.py" >"$WORK/copy-mut.out" 2>&1; then
-    mut_rc=0
-else
-    mut_rc=$?
-fi
-if [ "$clean_rc" -eq 0 ] && [ "$mut_rc" -eq 1 ]; then
-    row copy-parity "PASS  clean copy rc=0, mutated copy rc=1"
-    passed=$((passed + 1))
-else
-    row copy-parity "FAULT clean copy rc=$clean_rc (want 0), mutated rc=$mut_rc (want 1)"
-    head -5 "$WORK/copy-clean.out" "$WORK/copy-mut.out"
     failed=$((failed + 1))
+else
+    COPY="$WORK/lane/wizard-work/quill"
+    if python3 "$COPY/verify_draft_compliance.py" >"$WORK/copy-clean.out" 2>&1; then
+        clean_rc=0
+    else
+        clean_rc=$?
+    fi
+    # move one row's line count in the COPY's TSV: the copy must notice
+    awk -F'\t' 'BEGIN{OFS="\t"} NR==3{$2=$2+1} {print}' \
+        "$COPY/draft-compliance-report-2026-10-31.tsv" >"$WORK/mut.tsv" \
+        && mv "$WORK/mut.tsv" "$COPY/draft-compliance-report-2026-10-31.tsv"
+    if python3 "$COPY/verify_draft_compliance.py" >"$WORK/copy-mut.out" 2>&1; then
+        mut_rc=0
+    else
+        mut_rc=$?
+    fi
+    if [ "$clean_rc" -eq 0 ] && [ "$mut_rc" -eq 1 ]; then
+        row copy-parity "PASS  HEAD copy rc=0, mutated copy rc=1"
+        passed=$((passed + 1))
+    else
+        row copy-parity "FAULT clean copy rc=$clean_rc (want 0), mutated rc=$mut_rc (want 1)"
+        head -5 "$WORK/copy-clean.out" "$WORK/copy-mut.out"
+        failed=$((failed + 1))
+    fi
 fi
 
 echo