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>

agents/brief-reviewer.md

@@ -61,6 +61,9 @@ is one test-runner invocation with no pipe, redirect or `&&`: `npm test`,
 `npm run <script>`, `node --test <file>`, `vitest`, `jest`, `pytest`,
 `python -m pytest`, `uv run pytest`, `cargo test`, `go test`, `make test`,
 `bash tests/<script>.sh` (or `/bin/bash tests/<script>.sh`), or `git status|log|diff|show|ls-files`.
+It runs with no shell, as plain words: no quote, `$`, brace, leading `~` or
+`@`, no glob outside `node --test`, no `..` or absolute path, and only the
+runner's read-only options.
 Anything else — the product's own binary (`node bin/x.mjs …`), `jq`, `grep`,
 `git grep`, a pipe — is reported NOT RUN. Never PROPOSE such a command as a
 criterion. When a criterion needs one, propose wrapping it in a script under