fix(#3477): run untrusted key_links patterns on a linear-time engine (#3496)

`cmdVerifyKeyLinks` compiled `must_haves.key_links[].pattern` from plan frontmatter with `new RegExp()` and tested it against whole file contents, so a nested-quantifier pattern such as `(a+)+$` hung `verify-phase` indefinitely (CWE-1333). JavaScript has no regex-execution timeout.

Untrusted patterns now run on RE2 (re2js), whose match time is linear in input length — the class is closed by the engine, not by a heuristic screen. The screen lost in the ADR-0174 consolidation was deliberately NOT restored: it never worked, since `(a|a)*$`, `((a+))+$`, `(a+){2,}$` and `(a{1,3})+$` all evade it. A refused pattern's matcher returns false for every input, so it cannot report a match no matter what the caller does.

The engine is vendored at gsd-core/bin/lib/vendor/re2js.cjs because gsd-core/bin/** is copied into installed trees with no node_modules; runtime dependencies are unchanged. New ESLint rule local/no-external-require-in-bin enforces that invariant, which had been documented in a comment since the #3024/#2071 bug class and enforced nowhere.

Backreferences and look-around are unsupported by RE2 by construction — disclosed in a Changed changeset.

Closes #3477

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

package.json

@@ -74,6 +74,7 @@
     "fast-check": "^4.8.0",
     "globals": "^16.5.0",
     "js-yaml": "^4.3.1",
+    "re2js": "^2.8.6",
     "typescript": "^6.0.3",
     "typescript-eslint": "^8.60.0"
   },
@@ -116,7 +117,7 @@
     "lint:table-schema-drift": "node scripts/lint-table-schema-drift.cjs",
     "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: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-emitted-drift-ack.cjs && node scripts/lint-portable-timeout.cjs && node scripts/validate-registry.cjs && node scripts/lint-table-schema-drift.cjs && node scripts/lint-fix-has-regression-test.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-completion-ratio-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",
+    "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-emitted-drift-ack.cjs && node scripts/lint-portable-timeout.cjs && node scripts/validate-registry.cjs && node scripts/lint-table-schema-drift.cjs && node scripts/lint-fix-has-regression-test.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-completion-ratio-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",
     "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",