fix(#663): resolve open CodeQL/Dependabot security alerts (ReDoS, prototype pollution, workflow perms, qs DoS) (#665)

* fix(#663): resolve open CodeQL/Dependabot security alerts

- ReDoS: collapse ambiguous nested quantifiers in phase-heading regexes
  (verify/validate/commands) and the plan-filename lookahead (phase) to
  provably-equivalent non-backtracking forms
- prototype pollution: guard __proto__/constructor/prototype in setConfigValue
- remove dead no-op .replace(/-/g,'-') in phase.cts
- escape all regex metachars in bug-2839 test
- add contents:read permissions to security-scan + install-smoke workflows
- pin qs >= 6.15.2 via overrides (DoS GHSA)
- broaden prompt-injection allowlist to translated security-model docs

Closes #663

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* test(#663): regression tests for prototype-pollution guard and roadmap-phase ReDoS

Behavioral test that config-set rejects __proto__/constructor/prototype keys
without polluting Object.prototype, plus a ReDoS guard (timing-bound) and
behavior-preservation assertions for the collapsed phase-heading regexes.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* test(#663): make ReDoS regression assert structured result, not elapsed time

Replace elapsed-time assertions (which tripped local/no-elapsed-assertion
ESLint rule and were unsound for synchronous ReDoS) with structured-result
assertions on adversarial inputs: assert that malformed phase headings/
unchecked-item lines without a terminating colon/space yield an empty Set,
which is both the correct behavior and an exercise of the fixed linear regex
on the catastrophic-backtracking input shape.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* chore(#663): add Security changeset fragment for #665

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* test(#663): fold prototype-pollution regression into config.test.cjs

The standalone bug-663-config-prototype-pollution.test.cjs was a 9th
config-module test file, tripping lint-test-file-count (the allowlist is
ratcheted and must not grow). Consolidated into config.test.cjs instead.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

package-lock.json

@@ -5010,22 +5010,6 @@
         "node": ">= 16.0.0"
       }
     },
-    "node_modules/typed-rest-client/node_modules/qs": {
-      "version": "6.15.1",
-      "resolved": "https://registry.npmjs.org/qs/-/qs-6.15.1.tgz",
-      "integrity": "sha512-6YHEFRL9mfgcAvql/XhwTvf5jKcOiiupt2FiJxHkiX1z4j7WL8J/jRHYLluORvc1XxB5rV20KoeK00gVJamspg==",
-      "dev": true,
-      "license": "BSD-3-Clause",
-      "dependencies": {
-        "side-channel": "^1.1.0"
-      },
-      "engines": {
-        "node": ">=0.6"
-      },
-      "funding": {
-        "url": "https://github.com/sponsors/ljharb"
-      }
-    },
     "node_modules/typescript": {
       "version": "6.0.3",
       "resolved": "https://registry.npmjs.org/typescript/-/typescript-6.0.3.tgz",