refactor(simplify): one source per rule, shared test helpers, a faster isolation test [skip-docs]

/simplify over a97efb6..HEAD (the plan_version 1.9 / trial-4 delivery).

- coordinator-contract: engine names come from engine-findings ENGINES;
  one markedMajorCodeReview predicate under both lowering checks;
  isEngineFinding everywhere; the unreachable branch (c) of
  illegalBriefLowering folded into (e).
- armB workflow: RULE_KEYS = Object.keys(RULE_TIERS); the engine map is a
  literal pinned equal to ENGINES by the workflow test.
- plan-schema: usesFilesGrammar() is the one 1.9 check (validator, sweep,
  testFirstFiles, stepTestsOnlyFromFields); opensEntry built on opensChunk.
- plan-validator: one issue builder for the Files and Test first grammar.
- plan-scope-sweep: the 1.9 and the 6.2.0 reader are one if/else.
- artifact-commit: TRAILER_RE/trailerProblem no longer exported (no
  importer); the order comment says the CLI finds the repo root first.
- tests: the lock drivers in session-id-isolation (d) run side by side per
  mode (~100 s -> ~30 s); a shared artifact-repo helper; severityRank and
  extractFindingsBlock reused; childEnv(env) without a spread; one copy of
  the PLAN_VERSION_CURRENT check.

Plan readers: validator errors/warnings, plannedPaths, fieldPaths,
testFirstFiles and stepTestsOnlyFromFields compared byte for byte against
HEAD over 510 plans / 1692 steps plus 210 synthetic 1.7-1.9 cases: same.
Suite 2384 (2382/0/2).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

lib/validators/plan-validator.mjs

@@ -53,7 +53,7 @@ import { readFileSync, existsSync } from 'node:fs';
 import {
   sliceSteps, validatePlanHeadings, extractPlanVersion, extractPlanCeremony,
   parseStepFields, findSection, splitSections, findModuleCycle, parseMermaid, fencedBlocks,
-  versionAtLeast, PLAN_VERSION_CURRENT, PLAN_VERSIONS_SUPPORTED, CEREMONY_VALUES,
+  versionAtLeast, usesFilesGrammar, PLAN_VERSION_CURRENT, PLAN_VERSIONS_SUPPORTED, CEREMONY_VALUES,
   ON_FAILURE_ACTIONS, onFailureAction, stepTestsOnlyFromFields, entryPaths, untickedPaths,
   testFirstFileEntries, testFirstFiles,
 } from '../parsers/plan-schema.mjs';
@@ -77,7 +77,7 @@ const BACKTICKED = /`[^`\n]+`/;
 function checkSteps(sections, planVersion) {
   const out = [];
   let endToEnd = 0;
-  const grammar = versionAtLeast(planVersion, '1.9');
+  const grammar = usesFilesGrammar(planVersion);
   for (const s of sections) {
     const f = parseStepFields(s.body);
     const tf = f.get('Test first');
@@ -217,42 +217,38 @@ function checkRecovery(sections, opts, planVersion) {
  * names no file. Each `Test first:` `File:` line (plan-schema
  * `testFirstFileEntries`) is one entry under the same grammar.
  */
+// How checkPathGrammar words an issue in each of the two places the grammar applies.
+const FILES_WORDING = {
+  subject: 'a `Files:` entry', none: '`Files:` names no file', spans: 'an entry are its files',
+  opens: 'each `Files:` entry opens with its backticked path(s)',
+  example: '`` `src/a.mjs` - the parser ``', tail: ' A step that changes no file names none.',
+};
+const TEST_FIRST_WORDING = {
+  subject: 'a `Test first:` `File:` line', none: 'a `Test first:` `File:` line names no file',
+  spans: 'the `File:` line are the test files', opens: 'the `File:` line opens with its backticked test file(s)',
+  example: '`` File: `tests/a.test.mjs` (new) ``', tail: '',
+};
+
+function pathGrammarIssue(n, code, shown, w) {
+  if (code === 'PLAN_STEP_PATH_NOT_A_PATH') {
+    return issue(code, `Step ${n}: ${w.subject} opens with a backticked span that is no path: ${shown}`,
+      `plan_version 1.9: the leading backticked spans of ${w.spans}; a call (\`parse()\`), an option ` +
+        'or a URL is description and goes after the path.');
+  }
+  return issue('PLAN_STEP_PATH_NOT_FIRST',
+    shown === '' ? `Step ${n}: ${w.none}` : `Step ${n}: ${w.subject} does not open with a backticked path: ${shown}`,
+    `plan_version 1.9: ${w.opens}, separated by commas or spaces; the description follows (${w.example}).${w.tail}`);
+}
+
 function checkPathGrammar(sections) {
   const out = [];
   for (const s of sections) {
     const f = parseStepFields(s.body);
-    const { issues } = entryPaths(f.has('Files') ? f.get('Files').text : '');
-    for (const i of issues) {
-      if (i.code === 'PLAN_STEP_PATH_NOT_A_PATH') {
-        out.push(issue('PLAN_STEP_PATH_NOT_A_PATH',
-          `Step ${s.n}: a \`Files:\` entry opens with a backticked span that is no path: ${i.entry}`,
-          'plan_version 1.9: the leading backticked spans of an entry are its files; a call (`parse()`), an option ' +
-            'or a URL is description and goes after the path.'));
-      } else {
-        out.push(issue('PLAN_STEP_PATH_NOT_FIRST',
-          i.entry === ''
-            ? `Step ${s.n}: \`Files:\` names no file`
-            : `Step ${s.n}: a \`Files:\` entry does not open with a backticked path: ${i.entry}`,
-          'plan_version 1.9: each `Files:` entry opens with its backticked path(s), separated by commas or spaces; ' +
-            'the description follows (`` `src/a.mjs` - the parser ``). A step that changes no file names none.'));
-      }
+    for (const i of entryPaths(f.has('Files') ? f.get('Files').text : '').issues) {
+      out.push(pathGrammarIssue(s.n, i.code, i.entry, FILES_WORDING));
     }
     for (const entry of testFirstFileEntries(f)) {
-      for (const i of entryPaths(entry).issues) {
-        if (i.code === 'PLAN_STEP_PATH_NOT_A_PATH') {
-          out.push(issue('PLAN_STEP_PATH_NOT_A_PATH',
-            `Step ${s.n}: a \`Test first:\` \`File:\` line opens with a backticked span that is no path: ${entry}`,
-            'plan_version 1.9: the leading backticked spans of the `File:` line are the test files; a call ' +
-              '(`parse()`), an option or a URL is description and goes after the path.'));
-        } else {
-          out.push(issue('PLAN_STEP_PATH_NOT_FIRST',
-            entry === ''
-              ? `Step ${s.n}: a \`Test first:\` \`File:\` line names no file`
-              : `Step ${s.n}: a \`Test first:\` \`File:\` line does not open with a backticked path: ${entry}`,
-            'plan_version 1.9: the `File:` line opens with its backticked test file(s), separated by commas or ' +
-              'spaces; the description follows (`` File: `tests/a.test.mjs` (new) ``).'));
-        }
-      }
+      for (const i of entryPaths(entry).issues) out.push(pathGrammarIssue(s.n, i.code, entry, TEST_FIRST_WORDING));
     }
   }
   return out;
@@ -369,7 +365,7 @@ export function validatePlanContent(rawText, opts = {}) {
   warnings.push(...recovery.warnings);
 
   // The `Files:` grammar (decision 16): refused from 1.9, a warning below it.
-  if (versionAtLeast(planVersion, '1.9')) {
+  if (usesFilesGrammar(planVersion)) {
     const grammar = checkPathGrammar(sections);
     if (strict) errors.push(...grammar);
     else warnings.push(...grammar);
@@ -397,7 +393,7 @@ export function validatePlanContent(rawText, opts = {}) {
   if (stepsFrom !== null) {
     const appended = sections.filter((s) => Number(s.n) >= stepsFrom);
     const stepIssues = versionAtLeast(planVersion, '1.8') ? [] : [
-      ...checkSteps(appended, planVersion).filter((i) => i.code !== 'PLAN_NO_END_TO_END'),
+      ...checkSteps(appended).filter((i) => i.code !== 'PLAN_NO_END_TO_END'),
       ...checkRunnable(text, appended, { cwd: opts.cwd, stepsOnly: true }),
     ];
     for (const s of appended) {