fix(migration): remediate 6 MAJOR + 3 MINOR trekreview findings + stale rename test

MAJOR
- 9e97cd5 40-validate-standalone.sh: route a target's sc2_gate to its dedicated
  gate (config-audit → 50-config-audit-sc2.sh), mirroring 99-dryrun.sh, so --all
  no longer falsely FAILs config-audit on the machine-locked v5.0.0 tests.
- 1708e90 99-dryrun.sh: assert EXACTLY one tag survives (F5); a partial tag-strip
  no longer silently reports the wrong tag via head -1.
- 4e494c8 99-dryrun.sh: capture the SC2 standalone failing set from the dry-run's
  own prepped extract ($dest), not the 40-validate side-effect clean room.
- aeb6292 00-preflight.sh: assert every map path is whitespace/glob-free, making
  the word-split path handling in 99-dryrun.sh sound.
- 5d112cb extract the SC6 DROP + SC2 regression detectors into sc6-check.sh /
  sc2-regression.sh and add sc-checks.test.mjs — a negative test proving each
  detector FIRES (force-fresh re-extraction would undo a planted file-drop).
- 9e588ca 10-extract.sh re-asserts git filter-repo before use (self-heal runs
  preflight only on a missing mirror); RUNBOOK lists git-filter-repo + python3>=3.6.

MINOR
- bc0f8a7 plugin-map.json: reset ms-ai-architect blob_strip_safe to null
  (00-preflight.sh populates it per run).
- 8d649e9 99-dryrun.sh: gate SC6 behind extract success; a failed extract is
  labelled (extract failed), not a content DROP.
- 4044c49 99-dryrun.sh: guard mktemp — an empty capture is an error, not a
  false zero-regression PASS.

Also: 00-preflight.test.mjs asserted all 3 'renamed' plugins carry >=2 paths, but
llm-security became single-path in 836b8e9 (copilot was a coexisting plugin, not a
rename) — a stale pre-existing failure. Aligned the test to the ratified map and
added a positive single-path lock against re-introducing the 87-file-drop defect.

Verified: full dry-run 11/11, 0 pushes; sc-checks/99-dryrun/40-validate/00-preflight/
60-rewrite suites green.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

docs/marketplace-polyrepo-migration/migration/00-preflight.test.mjs

@@ -11,13 +11,18 @@ const map = JSON.parse(readFileSync(join(here, 'plugin-map.json'), 'utf8'));
 const targets = map.targets;
 const keys = Object.keys(targets);
 
-const RENAMED = ['voyage', 'llm-security', 'linkedin-studio'];
+// voyage ← ultraplan-local and linkedin-studio ← linkedin-thought-leadership are TRUE renames, so each
+// carries >=2 --path entries (F1). llm-security is NOT a rename: llm-security-copilot was a SEPARATE,
+// COEXISTING plugin, so llm-security is SINGLE-path (corrected 2026-06-17, commit 836b8e9) — a dual --path
+// there collided at the coexistence commits and dropped 87 files. The map is authoritative; this suite
+// tracks it.
+const RENAMED = ['voyage', 'linkedin-studio'];
 
 test('plugin-map.json parses and has exactly 11 targets (10 plugins + DS)', () => {
   assert.equal(keys.length, 11, `expected 11 targets, found ${keys.length}: ${keys.join(', ')}`);
 });
 
-test('the 3 renamed plugins each carry >=2 --path entries (F1)', () => {
+test('the renamed plugins (voyage, linkedin-studio) each carry >=2 --path entries (F1)', () => {
   for (const k of RENAMED) {
     assert.ok(targets[k], `missing renamed target ${k}`);
     assert.ok(
@@ -27,6 +32,15 @@ test('the 3 renamed plugins each carry >=2 --path entries (F1)', () => {
   }
 });
 
+test('llm-security is SINGLE-path — NOT a rename (copilot was a coexisting plugin, 836b8e9)', () => {
+  // Locks in the 87-file-drop correction: re-introducing a 2nd --path here would re-collide at the
+  // coexistence commits and silently drop files again.
+  assert.equal(
+    targets['llm-security'].paths.length, 1,
+    `llm-security must stay single-path (dual-path dropped 87 files), has ${targets['llm-security'].paths.length}`
+  );
+});
+
 test('every target repo_url is https:// (not ssh://) — F2 / #9740', () => {
   for (const k of keys) {
     assert.match(targets[k].repo_url, /^https:\/\/git\.fromaitochitta\.com\/open\//, `${k} repo_url not the expected HTTPS form`);