fix: round 5 of the release review of 6.3.0, the structural fix

Round 5 (v6.2.0..d37e538, WARN: 11 MAJOR, 2 MINOR). The patching did not
converge (the same two places every round), so the operator chose a
structural fix on 2026-10-11. Each change behind a test that failed first.

- A check runs with no shell. criteria-runner's runCommand starts the runner
  with the very words the screen checked (spawnSync(words[0], words.slice(1)),
  without NODE_TEST_CONTEXT); Phase 7 criteria, Regression: (its exec copy is
  gone, MINOR 0e98d5c7), proof of red, the done line and the test lock all
  run through it. No quote, glob, tilde or variable can rewrite a checked
  word any more. The screen stays and says why: a word that means something
  else in a shell (quote, backslash, $, brace, leading ~) is refused; a glob
  reaches only node --test, which expands its own patterns (sh read
  `tests/.?/` as `tests/../`); no path climbs out with .. or starts at /;
  a word starting with @ is refused (pytest reads @file as more arguments).
- The K6 plan-file sweep has v6.2.0's own Files: reader again (516dffa):
  backticked paths, and plain words only in a field without them. The
  shared reader from round 3 planned directories a description named and
  dropped paths v6.2.0 planned. fieldPaths stays for the tests-only check,
  with a path test on spans (`parse()`, `p.parse()` are no paths), plain
  descriptions ignored when the field has backticked paths, dotfiles,
  backslash paths and glued spans read.
- Skill frontmatter reads a value as YAML does: trailing space is nothing,
  and a comment ends a plain value, a flow list or a block indicator
  (`model: opus # pinned`). A comment that cuts a plain description, or is
  the whole value, is still a hazard.
- release-check reads the diff with --no-renames: a test moved into an
  allowed place after the review shows as removed.
- The example plan's step 2 heading no longer says "must FAIL initially";
  steps 1-2 keep the tests-only warning (operator 2026-10-09, 73262b6).

Open: MINOR c1fef1ad (one shared isMain helper) is not in this round.
Measured: 0 of 463 Files: fields with backticked paths (520 fields in 182
plans across the marketplace repos) carry another path-like word.

Suite 2185 (2183/0/2).

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

lib/verification/done-line.mjs

@@ -23,8 +23,8 @@ import { appendFileSync, existsSync, readFileSync, realpathSync } from 'node:fs'
 import { spawnSync } from 'node:child_process';
 import { resolve } from 'node:path';
 import { fileURLToPath } from 'node:url';
-import { allowedCommand, screenCommand } from './criteria-runner.mjs';
-import { commandEnv, DEFAULT_TIMEOUT_MS, repoRoot } from './red-proof.mjs';
+import { allowedCommand, runCommand, screenCommand } from './criteria-runner.mjs';
+import { DEFAULT_TIMEOUT_MS, repoRoot } from './red-proof.mjs';
 
 export function doneLineRe(step, commit) {
   const sha = commit ? String(commit).replace(/[^0-9a-f]/g, '') : '[0-9a-f]{40}';
@@ -55,7 +55,8 @@ export function writeDoneLine({ cwd, step, cmd, report, timeoutMs = DEFAULT_TIME
   if (!screen.allowed) return { status: 'not-run', reason: `command blocked: ${screen.rule}` };
   const head = spawnSync('git', ['rev-parse', '--verify', '--quiet', 'HEAD'], { cwd: dir, encoding: 'utf8' });
   if (head.status !== 0) return { status: 'not-run', reason: `no git HEAD in ${dir}` };
-  const r = spawnSync('/bin/sh', ['-c', cmd], { cwd: dir, env: commandEnv(), encoding: 'utf8', timeout: timeoutMs, maxBuffer: 64 * 1024 * 1024 });
+  // No shell: the words the screen checked are the words that run.
+  const r = runCommand(cmd, { cwd: dir, timeoutMs });
   if (r.error || r.status === null || r.status === 126 || r.status === 127) {
     return { status: 'not-run', reason: `the command did not run to an exit code (${r.error?.message ?? r.signal ?? `exit ${r.status}`})`, exit: r.status };
   }