phase 1.6 BIPA: scrum-driven fixes

Per 2026-05-03 phase_1_6_bipa_gates scrum (13 findings, 0 convergent).
1 BLOCK verified false positive, 4 real fixes shipped:

False positive (verified):
- opus BLOCK on attest:55 — claimed `set -uo pipefail` without `-e`
  makes the post-python3 `if [ $? -ne 0 ]` check unreachable. Verified
  WRONG: `X=$(false); echo $?` prints 1. Bash propagates command-
  substitution exit through $? on the assignment line. The check IS
  the python3 exit gate. Inline comment added to the script noting
  the false positive so future scrums don't re-flag.

Real fixes:
1. opus WARN attestation:18 — schema fingerprint hashed names ONLY,
   missing column-type changes. A column repurposed to hold base64
   photo bytes under its existing name would pass undetected. Now
   hashes "name<TAB>type<TAB>nullable=bool" per row. Re-run produced
   evidence SHA-256 1fdcc9f1... (vs old 230fffeb..., reflecting the
   broader fingerprint scope).

2. opus WARN gate_4_test:60 — definition regex didn't catch
   object-literal property forms (`const t = { FEMALE_NAMES: [...] }`)
   or TypeScript class fields (`class L { public NAMES_X: string[] = [] }`).
   Added two new patterns + a regression test
   (Gate 4: object-literal and class-field bypasses are caught) that
   exercises 5 bypass forms. 4/4 tests green; 1 minor regex tweak
   needed mid-fix to handle single-line class bodies.

3. kimi WARN python3-reliance — script assumed pyarrow installed and
   would emit a stack trace into the attestation if not. Added
   `python3 -c "import pyarrow"` gate at top with clean install
   instructions on failure.

4. opus INFO PHASE_1_6:200 — item 7 (training) silently dropped from
   blocking set with bare "deferred" rationale. Now explicitly states
   the deferral is conditional on small operator population (J + 1-2
   named ops); item 7 re-promotes to blocking if population grows.
   ⚖ COUNSEL marker added.

Skipped (acceptable as ⚖ COUNSEL placeholders by design):
- kimi WARN consent template:30-day-SLA (counsel decides number)
- kimi WARN consent template:email-placeholder (counsel supplies)
- kimi WARN parquet absence (env override exists; redeployment-aware)
- kimi INFO runbook manual-erasure (marked TODO when /erase ships)
- qwen INFO doc path/status nits (already addressed by file moves)

Tests: 4/4 Gate 4 absence test (incl. new bypass-coverage), 3/3
attestation evidence checks pass on live data.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

scripts/staffing/attest_pre_identityd_biometric_state.sh

@@ -34,6 +34,17 @@
 set -uo pipefail
 cd "$(dirname "$0")/../.."
 
+# Dependency gate: pyarrow is required to read the parquet schema. Fail
+# fast with a clear message rather than letting python3 -c emit a stack
+# trace that gets captured into the attestation as "evidence". (Caught
+# 2026-05-03 kimi scrum WARN python3-reliance.)
+if ! python3 -c "import pyarrow" 2>/dev/null; then
+  echo "[attest] FAIL: python3 -c 'import pyarrow' failed." >&2
+  echo "[attest]   pyarrow is required to verify workers_500k.parquet schema." >&2
+  echo "[attest]   Install with: pip install pyarrow" >&2
+  exit 2
+fi
+
 DATE="${OVERRIDE_DATE:-$(date -u +%Y-%m-%d)}"
 OUT_DIR="docs/attestations"
 OUT="$OUT_DIR/BIPA_PRE_IDENTITYD_ATTESTATION_${DATE}.md"
@@ -62,12 +73,20 @@ if [ ! -r "$WORKERS_PARQUET" ]; then
   rm -f "$EVIDENCE"
   exit 2
 fi
+# Hash NAME + TYPE + nullability per column, not just names. A schema
+# fingerprint over names alone would not invalidate if a column got
+# repurposed (e.g. resume_text reused to hold base64 photo bytes under
+# its existing name). Including types catches that class of evasion.
+# (Caught 2026-05-03 opus scrum WARN on attestation:18.)
 SCHEMA=$(python3 -c "
 import sys, pyarrow.parquet as pq
 schema = pq.read_schema('$WORKERS_PARQUET')
 for f in schema:
-    print(f.name)
+    print(f'{f.name}\t{f.type}\tnullable={f.nullable}')
 " 2>&1)
+# Bash assigns + propagates the substitution's exit through \$?.
+# Verified: X=\$(false); echo \$? -> 1. opus 2026-05-03 BLOCK on this
+# location was a false positive — the check IS the python3 exit gate.
 if [ $? -ne 0 ]; then
   echo "[attest] FAIL: schema read error: $SCHEMA" >&2
   rm -f "$EVIDENCE"