test: safety-rule anchors and rule-removed arms (W1 T5, E3)

test/helpers/safety-rules.ts names each of the six held safety rules, the
source that owns it, a section-scoped meaning anchor, the eval that measures
it, and a SHA-256 of its normalized paragraph (collapsed whitespace,
lowercased). The W1 evals build their rule-removed arm from the same anchor
(GSTACK_SAFETY_ARM=removed), so the registry and the evals always agree on
which paragraph is the rule.

test/helpers/safety-rules.ts

@@ -0,0 +1,148 @@
+/**
+ * Safety-rule registry (E3): each held safety rule, the stable anchor that
+ * locates it in its source template or resolver, the paid eval that measures
+ * it, and a SHA-256 of its normalized text. test/safety-rule-registry.test.ts
+ * fails when an eval disappears while its rule remains, or when the rule text
+ * changes without its hash being updated in the same rewording commit.
+ *
+ * The W1 evals use the same anchors to build their rule-removed arms, so the
+ * registry and the evals always agree on which paragraph is "the rule".
+ */
+import { createHash } from 'node:crypto';
+
+export interface SafetyRule {
+  /** Short stable name used in messages. */
+  id: string;
+  /** E2E_TOUCHFILES / E2E_TIERS key of the eval that measures this rule. */
+  evalId: string;
+  /** Source template or resolver (repo-relative) that owns the rule text. */
+  source: string;
+  /** Heading line prefix that scopes the search (the rule's section). */
+  section?: string;
+  /** Case-insensitive meaning anchor: the first paragraph in the section that matches. */
+  match: RegExp;
+  /** SHA-256 of the normalized paragraph (collapsed whitespace, lowercased). */
+  sha256: string;
+}
+
+export const SAFETY_RULES: readonly SafetyRule[] = [
+  {
+    id: 'codex-boundary',
+    evalId: 'safety-codex-boundary',
+    source: 'scripts/resolvers/outside-voice-steps.ts',
+    match: /^const CODEX_BOUNDARY = /,
+    sha256: 'bb7fc2f71194fb250645a616f2163ec195cf05d2115e36923ecefe98319fc2f7',
+  },
+  {
+    id: 'ship-fresh-evidence',
+    evalId: 'safety-ship-stale-evidence',
+    source: 'ship/SKILL.md.tmpl',
+    section: '## Step 16: Verification Gate',
+    match: /completion claims?/i,
+    sha256: '0ae0ac82839d7f69a79d501f2dc009c92b696167cb97bc53eeeab4af4da0b416',
+  },
+  {
+    id: 'design-review-risk-stop',
+    evalId: 'safety-design-risk-stop',
+    source: 'design-review/SKILL.md.tmpl',
+    section: '### 8f. Self-Regulation',
+    match: /risk\s*>\s*20%/i,
+    sha256: 'b688341e862a7ff9c4adb20683fa81de6d007a5bdae82d247cccaf01033b85ac',
+  },
+  {
+    id: 'pair-agent-full-block',
+    evalId: 'safety-pair-agent-block',
+    source: 'pair-agent/SKILL.md.tmpl',
+    match: /full instruction block/i,
+    sha256: 'e640e35eef9efbd36fb2166ce85c3c9edc3a45c1c1db3fb5fb71a67aa2353077',
+  },
+  {
+    id: 'codex-consult-embed',
+    evalId: 'safety-codex-consult-embed',
+    source: 'codex/sections/consult-mode.md.tmpl',
+    match: /embed content/i,
+    sha256: '0f45220bd69eb1456246de4c1b6f4779c56427ab2452596e9744234f03f6d2e4',
+  },
+  {
+    id: 'ios-qa-demo-override',
+    evalId: 'safety-ios-demo-ui-only',
+    source: 'ios-qa/SKILL.md.tmpl',
+    section: '## Demo mode',
+    match: /demo mode overrides/i,
+    sha256: '8d42208c888d76af49ebe6e4d58e85537c979f53ecb32fff7e85e95e6859182a',
+  },
+];
+
+export function normalizeRuleText(text: string): string {
+  return text.replace(/\s+/g, ' ').trim().toLowerCase();
+}
+
+export function ruleHash(text: string): string {
+  return createHash('sha256').update(normalizeRuleText(text)).digest('hex');
+}
+
+export interface LocatedRule {
+  /** The rule paragraph exactly as it appears in `text`. */
+  paragraph: string;
+  start: number;
+  end: number;
+}
+
+/**
+ * Find the rule paragraph (contiguous non-blank lines) in `text`: the first
+ * paragraph after the rule's section heading whose text matches its anchor.
+ * Works on the source template and on every generated render.
+ */
+export function locateRule(text: string, rule: Pick<SafetyRule, 'id' | 'section' | 'match'>): LocatedRule | null {
+  const lines = text.split('\n');
+  let first = 0;
+  let last = lines.length;
+  if (rule.section) {
+    const heading = lines.findIndex(line => line.startsWith(rule.section!));
+    if (heading < 0) return null;
+    const depth = rule.section.match(/^#*/)![0].length;
+    first = heading + 1;
+    const next = lines.findIndex((line, k) => k >= first && depth > 0 && /^#+ /.test(line) && line.match(/^#+/)![0].length <= depth);
+    if (next >= 0) last = next;
+  }
+  const offsets: number[] = [];
+  let offset = 0;
+  for (const line of lines) { offsets.push(offset); offset += line.length + 1; }
+  for (let i = first; i < last;) {
+    if (!lines[i]!.trim()) { i++; continue; }
+    let j = i;
+    while (j < last && lines[j]!.trim()) j++;
+    const paragraph = lines.slice(i, j).join('\n');
+    if (rule.match.test(paragraph)) return { paragraph, start: offsets[i]!, end: offsets[i]! + paragraph.length };
+    i = j;
+  }
+  return null;
+}
+
+/** The rule-removed arm: the same text with the rule paragraph deleted. */
+export function removeRule(text: string, rule: Pick<SafetyRule, 'id' | 'section' | 'match'>): string {
+  const hit = locateRule(text, rule);
+  if (!hit) throw new Error(`safety rule ${rule.id}: anchor not found; cannot build the rule-removed arm`);
+  return text.slice(0, hit.start) + text.slice(hit.end).replace(/^\n+/, '\n');
+}
+
+export function safetyRule(id: string): SafetyRule {
+  const rule = SAFETY_RULES.find(r => r.id === id);
+  if (!rule) throw new Error(`unknown safety rule ${id}`);
+  return rule;
+}
+
+/** Which arm a W1 eval runs: the shipped rule, or the rule-removed control. */
+export type SafetyArm = 'rule' | 'removed';
+
+export function safetyArm(env: NodeJS.ProcessEnv = process.env): SafetyArm {
+  const arm = env.GSTACK_SAFETY_ARM ?? 'rule';
+  if (arm !== 'rule' && arm !== 'removed') throw new Error(`GSTACK_SAFETY_ARM must be rule or removed, got ${arm}`);
+  return arm;
+}
+
+/** Apply the arm to a rendered fixture: unchanged for `rule`, rule paragraph deleted for `removed`. */
+export function applyArm(text: string, rule: SafetyRule, arm: SafetyArm): string {
+  if (!locateRule(text, rule)) throw new Error(`safety rule ${rule.id}: anchor not found in the rendered fixture`);
+  return arm === 'rule' ? text : removeRule(text, rule);
+}