test(3596): adversarial security/prompt-injection abuse suite (#3654)

* test(3596): adversarial security/prompt-injection abuse suite

Adds `tests/security-prompt-injection.test.cjs` and a fixtures
directory at `tests/fixtures/adversarial/security/` covering the
attack classes enumerated in #3596:

  - Command substitution / backticks / heredoc payloads in workstream
    names — sentinel-file probes prove no shell is spawned, slugifier
    neutralises the input.
  - Path traversal through `--ws` and slash-bearing workstream names —
    rejected with structured `--json-errors` payload, no stack trace,
    no filesystem mutation outside the project root.
  - Fake `<system>` / `[SYSTEM]` / `<<SYS>>` / `[INST]` boundary tags —
    sanitizeForPrompt neutralises every form; structural negative
    property locked across all six styles in one place.
  - Zero-width / bidi-override codepoints — stripped per the documented
    codepoint set; asserted via codePoint inspection, not regex
    literals.
  - Hostile read of CONTEXT.md / PLAN.md / ROADMAP.md fixtures —
    `gsd-read-injection-scanner.js` surfaces the advisory; excluded
    paths and non-Read tools stay silent; malformed JSON does not
    crash the hook.
  - Hostile write of `.planning/` files — `gsd-prompt-guard.js` emits
    a `PreToolUse` advisory; non-Write/Edit tools stay silent.
  - Fake `ghp_*` / `sk-*` env tokens — never echoed in CLI stdout or
    stderr under hostile inputs; covered under
    `// allow-test-rule: structural-regression-guard` because the only
    way to assert byte-level absence is `.includes(token)` against the
    captured streams.
  - `validatePath`, `validateShellArg`, `validatePhaseNumber`,
    `validateFieldName` — focused negative-input contract pins.

Pinned behavior gaps (documented, NOT fixed in this PR):

  - `<instructions>` is intentionally whitelisted by both the scanner
    and the sanitiser (GSD's own prompt scaffolding). Two REGRESSION
    GUARD tests lock that contract.
  - The current `scanForInjection` does NOT flag malicious markdown
    links (javascript:/data:/embedded-credentials URLs). PINNED with
    negative-proof so any future scope extension fails the assertion
    and forces a deliberate update to the acceptance map.
  - `prompt-builder.ts` does not yet wrap plan/context markdown in an
    "untrusted data" envelope. That seam lives on the TS side and is
    covered by `sdk/src/prompt-builder.test.ts`; out of scope for a
    CJS test file. Mentioned in the file header.

Verification:

  - `node --test tests/security-prompt-injection.test.cjs` → 73 tests
    pass.
  - `node scripts/lint-no-source-grep.cjs` → 0 violations across
    546 test files (one `allow-test-rule: structural-regression-guard`
    annotation on this file for the token-absence assertions).
  - `node scripts/run-tests.cjs` → 9730 tests pass, 0 fail.

Refs #3596

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* fix(3596): allow adversarial fixtures in scan + harden graphify status parse

* fix(3596): skip adversarial security fixtures in secret scan

---------

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

scripts/prompt-injection-scan.sh

@@ -77,13 +77,15 @@ ALLOWLIST=(
   'hooks/gsd-prompt-guard.js'
   'hooks/gsd-read-injection-scanner.js'
   'tests/read-injection-scanner.test.cjs'
+  'tests/security-prompt-injection.test.cjs'
+  'tests/fixtures/adversarial/security/'
   'SECURITY.md'
 )
 
 is_allowlisted() {
   local file="$1"
   for allowed in "${ALLOWLIST[@]}"; do
-    if [[ "$file" == *"$allowed" ]]; then
+    if [[ "$file" == *"$allowed"* ]]; then
       return 0
     fi
   done

scripts/secret-scan.sh

@@ -107,6 +107,8 @@ should_skip_file() {
   case "$file" in
     */secret-scan.sh) return 0 ;;
     */security-scan.test.cjs) return 0 ;;
+    */security-prompt-injection.test.cjs) return 0 ;;
+    tests/fixtures/adversarial/security/*|*/tests/fixtures/adversarial/security/*) return 0 ;;
   esac
   return 1
 }