chore(#4394): lint allowed-tools parity — Bash without Grep (#4431)

gen-plugin-skills.cjs --check already guarantees skills/*/SKILL.md matches
what commands/gsd/*.md generates, so the two trees cannot silently diverge
FROM EACH OTHER. Nothing guarded the shape #3085 actually found: a command
shipping Bash without Grep purely by omission, identical in both trees and
therefore invisible to a parity check that only compares them to each other.
That drift ran until 29 of 71 skills lacked a tool most of their siblings
declared, and a manual audit — not a gate — is what surfaced it.

Detection only: the lint never edits a command's allowed-tools.

Two failure classes, not one. Violations are the rule itself. Stale
exemptions are the other half: an entry whose command is gone, or which no
longer declares Bash without Grep, fails just as loudly. An exemption list
that can only grow becomes a list of things nobody re-examined, and a
pre-forgiven command silently absorbs the next omission.

That check earned its keep immediately. #4394 named eight exemptions from the
#3085 review — the six ns-* dispatchers, help, and surface — and seven of
them do not declare Bash at all, so the rule never reaches them. Listing them
would have pre-forgiven seven commands for a condition none of them has. Only
surface needs an entry.

The tests drive synthetic fixtures rather than the live corpus: asserting
"the real tree is clean" would say nothing about whether the rule can detect
anything, which is the exact failure mode this lint exists to close. The one
live-corpus arm asserts no stale exemptions — a property of this script's own
list — and deliberately does not pin a violation count, which would make it a
baseline every fix has to update.

Co-authored-by: Tom Boucher <trekkie@nomorestars.com>

package.json

@@ -122,7 +122,7 @@
     "lint:frontmatter-scalar-broad-grep": "node scripts/lint-frontmatter-scalar-broad-grep.cjs",
     "lint:removed-but-needed": "node scripts/lint-removed-but-needed.cjs",
     "lint:response-language": "node scripts/lint-response-language-coverage.cjs",
-    "lint:ci": "npm run lint && npm run lint:skill-deps && npm run lint:generated-sync && node scripts/lint-test-file-count.cjs && node scripts/lint-command-contract.cjs && node scripts/lint-pr-check-project-dir.cjs && npm run lint:legacy-name && node scripts/lint-regression-test-names.cjs && node scripts/lint-allow-test-rule-refs.cjs && node scripts/lint-resolution-provenance.cjs && node scripts/lint-portable-timeout.cjs && node scripts/lint-portable-grep.cjs && node scripts/validate-registry.cjs && node scripts/lint-table-schema-drift.cjs && node scripts/lint-fix-has-regression-tests.cjs && node scripts/lint-example-parser-parity.cjs && node scripts/lint-docs-command-form.cjs && node scripts/lint-plan-count-drift.cjs && node scripts/lint-milestone-window-drift.cjs && node scripts/lint-phase-enumeration-drift.cjs && node scripts/lint-planning-prompt-drift.cjs && node scripts/lint-unreachable-guard-drift.cjs && node scripts/lint-completion-ratio-drift.cjs && node scripts/lint-slug-derivation-drift.cjs && node scripts/lint-state-field-drift.cjs && node scripts/lint-state-write-path-drift.cjs && node scripts/lint-completion-predicate-drift.cjs && node scripts/lint-planning-snapshot-bypass-drift.cjs && node scripts/lint-health-diagnostic-rule-table.cjs && node scripts/lint-planning-artifact-writer-drift.cjs && node scripts/lint-frontmatter-scalar-broad-grep.cjs && node scripts/lint-removed-but-needed.cjs && node scripts/lint-no-adhoc-regex-escape.cjs && node scripts/lint-vendored-deps.cjs && node scripts/lint-docs-guard-registration.cjs && node scripts/lint-source-test-name-collision.cjs && npm run lint:hooks-runtime-build-seam && node scripts/check-contract-drift.cjs && node scripts/lint-mutation-test-derivation-drift.cjs && node scripts/lint-seam-enforcement.cjs && node scripts/lint-workflow-shellcheck.cjs && npm run lint:response-language",
+    "lint:ci": "npm run lint && npm run lint:skill-deps && npm run lint:generated-sync && node scripts/lint-test-file-count.cjs && node scripts/lint-command-contract.cjs && node scripts/lint-pr-check-project-dir.cjs && npm run lint:legacy-name && node scripts/lint-regression-test-names.cjs && node scripts/lint-allow-test-rule-refs.cjs && node scripts/lint-resolution-provenance.cjs && node scripts/lint-portable-timeout.cjs && node scripts/lint-portable-grep.cjs && node scripts/lint-allowed-tools-parity.cjs && node scripts/validate-registry.cjs && node scripts/lint-table-schema-drift.cjs && node scripts/lint-fix-has-regression-tests.cjs && node scripts/lint-example-parser-parity.cjs && node scripts/lint-docs-command-form.cjs && node scripts/lint-plan-count-drift.cjs && node scripts/lint-milestone-window-drift.cjs && node scripts/lint-phase-enumeration-drift.cjs && node scripts/lint-planning-prompt-drift.cjs && node scripts/lint-unreachable-guard-drift.cjs && node scripts/lint-completion-ratio-drift.cjs && node scripts/lint-slug-derivation-drift.cjs && node scripts/lint-state-field-drift.cjs && node scripts/lint-state-write-path-drift.cjs && node scripts/lint-completion-predicate-drift.cjs && node scripts/lint-planning-snapshot-bypass-drift.cjs && node scripts/lint-health-diagnostic-rule-table.cjs && node scripts/lint-planning-artifact-writer-drift.cjs && node scripts/lint-frontmatter-scalar-broad-grep.cjs && node scripts/lint-removed-but-needed.cjs && node scripts/lint-no-adhoc-regex-escape.cjs && node scripts/lint-vendored-deps.cjs && node scripts/lint-docs-guard-registration.cjs && node scripts/lint-source-test-name-collision.cjs && npm run lint:hooks-runtime-build-seam && node scripts/check-contract-drift.cjs && node scripts/lint-mutation-test-derivation-drift.cjs && node scripts/lint-seam-enforcement.cjs && node scripts/lint-workflow-shellcheck.cjs && npm run lint:response-language",
     "lint:allow-test-rule-refs": "node scripts/lint-allow-test-rule-refs.cjs",
     "lint:regression-names": "node scripts/lint-regression-test-names.cjs",
     "lint:descriptions": "node scripts/lint-descriptions.cjs",