fix(scan-orchestrator): honor .llm-security-ignore only for the caller's own working tree

A foreign or freshly-cloned scan target could ship its own
.llm-security-ignore with `**` and silently turn a real finding into
ALLOW (0 findings) -- only the undocumented envelope.suppressed count
revealed it. Same defect class the v8.0.0 commons-root fix closed: a
hostile repo should never be able to empty its own detection output.

Valgt X fordi Y: honor the ignore file only when realpath(target)
equals or is nested under realpath(process.cwd()), and never when the
target resolves under os.tmpdir() -- defense-in-depth for the case a
caller's own cwd happens to sit under tmpdir, matching where
git-clone.mjs materializes clones. A foreign target with an ignore
file now gets one stderr line saying it was not honored (loud, not
silent).

Red test first (tests/scanners/ignore-file-scope.test.mjs): a known
HIGH entropy finding (random-bytes base64, built at test time) that
must survive on a foreign/cloned target and stay suppressed on the
caller's own working tree. Verified red on b6edfa3, green after the
fix. Self-scan invariant reverified on three independent fresh clones
today: WARNING 61/100, 58 findings, 382 suppressed -- identical on
patched and unpatched clones, so the own-tree path is unchanged.

Suite 2276/2270 pass/0 fail/6 skip (jetbrains-parser after-hook flake
listed, not counted -- known). Golden unchanged (109/7/4, 61/61).
av-surface 6/6 green, unchanged.

Open, not fixed this session (scope was the ignore file only):
policy-loader.mjs's loadPolicy() also reads .llm-security/policy.json
from the scanned target, independently re-read by entropy-scanner.mjs
and signature-scanner.mjs -- same defect class, not yet measured red.
Logged in PLAN.md S3b for a follow-up order.

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

tests/scanners/ignore-file-scope.test.mjs

@@ -0,0 +1,143 @@
+// ignore-file-scope.test.mjs — .llm-security-ignore must never be honored
+// for a scanned target that is not the user's own working tree (S3b,
+// v8.1.0, 2026-09-22). scan-orchestrator.mjs reads .llm-security-ignore
+// straight from the SCANNED TARGET; a foreign/cloned target with `**` in
+// its own ignore file silently turned a real finding into ALLOW (only the
+// undocumented envelope.suppressed count revealed it). Same defect class as
+// the v8.0.0 commons-root fix: a hostile repo must not be able to empty its
+// own detection output by shipping an ignore file.
+//
+// Two scenarios, one real known finding (a random-bytes base64 string in a
+// .js file, which the entropy scanner classifies HIGH — verified directly
+// against entropy-scanner.mjs before this test was written):
+//   OWN working tree (spawn cwd === target, target arg '.', mirrors the real
+//     `node scanners/scan-orchestrator.mjs .` self-scan invocation): the
+//     `**` ignore rule MUST still suppress the finding — verdict ALLOW,
+//     envelope.suppressed === 1. This is the invariant S3b must not break.
+//     Deliberately placed OUTSIDE os.tmpdir() AND outside this repo's git
+//     working tree (a throwaway dir under $HOME, removed in `after()`): the
+//     fix excludes every path under the OS temp dir regardless of cwd, and a
+//     fixture nested inside this repo's own tree lets the git/permission/etc
+//     scanners pick up THIS repo's real history — either would fail this
+//     scenario for the wrong reason.
+//   FOREIGN target (spawn cwd elsewhere, target = absolute path under
+//     os.tmpdir(), i.e. what git-clone.mjs produces): the `**` ignore rule
+//     MUST NOT be honored — the HIGH finding must survive, verdict WARNING,
+//     envelope.suppressed falsy.
+
+import { describe, it, before, after } from 'node:test';
+import assert from 'node:assert/strict';
+import { resolve, dirname, join } from 'node:path';
+import { fileURLToPath } from 'node:url';
+import { spawn } from 'node:child_process';
+import { mkdtempSync, writeFileSync, rmSync } from 'node:fs';
+import { tmpdir, homedir } from 'node:os';
+import crypto from 'node:crypto';
+
+const __dirname = dirname(fileURLToPath(import.meta.url));
+const ORCHESTRATOR = resolve(__dirname, '../../scanners/scan-orchestrator.mjs');
+const REPO_ROOT = resolve(__dirname, '../..');
+
+// 72 random bytes -> base64 gives length 96, well past the entropy scanner's
+// HIGH threshold (H>=5.2, len>=40) regardless of exact byte values. Not a
+// real credential — a known-positive blob for the entropy scanner only.
+const HIGH_ENTROPY_BLOB = crypto.randomBytes(72).toString('base64');
+const IGNORE_ALL = '**\n';
+
+function writeFixture(dir) {
+  writeFileSync(join(dir, 'config.js'), `const payload = "${HIGH_ENTROPY_BLOB}";\nmodule.exports = { payload };\n`);
+  writeFileSync(join(dir, '.llm-security-ignore'), IGNORE_ALL);
+}
+
+function runOrchestrator(target, cwd) {
+  return new Promise((resolveP) => {
+    const stdout = [];
+    const stderr = [];
+    const child = spawn('node', [ORCHESTRATOR, target], {
+      cwd,
+      timeout: 180_000,
+      stdio: ['ignore', 'pipe', 'pipe'],
+    });
+    child.stdout.on('data', (c) => stdout.push(c));
+    child.stderr.on('data', (c) => stderr.push(c));
+    child.on('close', (code) => {
+      resolveP({
+        code: code ?? 1,
+        stdout: Buffer.concat(stdout).toString('utf8'),
+        stderr: Buffer.concat(stderr).toString('utf8'),
+      });
+    });
+  });
+}
+
+function findEntropyFindings(envelope) {
+  return envelope?.scanners?.entropy?.findings || [];
+}
+
+describe('.llm-security-ignore is scoped to the user\'s own working tree (S3b)', () => {
+  describe('OWN working tree: `node scanners/scan-orchestrator.mjs .` self-scan shape', () => {
+    let ownDir;
+    let result;
+    let env;
+
+    before(async () => {
+      // Outside os.tmpdir() AND outside this repo's git tree — see the
+      // file-header note.
+      ownDir = mkdtempSync(join(homedir(), '.ignore-scope-own-'));
+      writeFixture(ownDir);
+      // Mirrors the real self-scan invocation: cwd IS the target, arg is '.'.
+      result = await runOrchestrator('.', ownDir);
+      env = JSON.parse(result.stdout);
+    });
+
+    after(() => { rmSync(ownDir, { recursive: true, force: true }); });
+
+    it('suppresses the known HIGH entropy finding via the `**` ignore rule', () => {
+      assert.equal(findEntropyFindings(env).length, 0,
+        'entropy finding must be suppressed when the ignore file belongs to the scanned working tree');
+    });
+
+    it('reports the suppression count (loud, not silent)', () => {
+      assert.equal(env.suppressed, 1, 'envelope.suppressed must reflect the one suppressed finding');
+    });
+
+    it('verdict is ALLOW', () => {
+      assert.equal(env.aggregate.verdict, 'ALLOW');
+    });
+  });
+
+  describe('FOREIGN target: absolute path under os.tmpdir(), scanned from a different cwd', () => {
+    let foreignDir;
+    let result;
+    let env;
+
+    before(async () => {
+      foreignDir = mkdtempSync(join(tmpdir(), 'ignore-scope-foreign-'));
+      writeFixture(foreignDir);
+      // Mirrors a remote-clone scan: cwd is the repo, target is a foreign
+      // absolute path — exactly what git-clone.mjs hands the orchestrator.
+      result = await runOrchestrator(foreignDir, REPO_ROOT);
+      env = JSON.parse(result.stdout);
+    });
+
+    after(() => { rmSync(foreignDir, { recursive: true, force: true }); });
+
+    it('does NOT suppress the known HIGH entropy finding — the target\'s own ignore file is not honored', () => {
+      assert.equal(findEntropyFindings(env).length, 1,
+        'entropy finding must survive when the ignore file belongs to a foreign/cloned target, not the caller\'s own working tree');
+    });
+
+    it('reports no suppression', () => {
+      assert.ok(!env.suppressed, `envelope.suppressed must be falsy for a foreign target, got ${env.suppressed}`);
+    });
+
+    it('verdict is WARNING (the HIGH finding stands)', () => {
+      assert.equal(env.aggregate.verdict, 'WARNING');
+    });
+
+    it('logs a stderr line stating the ignore file was not honored, and why', () => {
+      assert.match(result.stderr, /\.llm-security-ignore.*ignored/i,
+        'a foreign-target ignore-file override must be loud, not silent');
+    });
+  });
+});