feat(llm-security): add /security ide-scan — VS Code / JetBrains extension prescan (v6.3.0)

New standalone scanner (prefix IDE) discovers installed VS Code extensions
across forks (Cursor, Windsurf, VSCodium, code-server, Insiders, Remote-SSH)
and runs 7 IDE-specific threat checks: blocklist match (CRITICAL),
theme-with-code, sideload (unsigned .vsix), dangerous uninstall hook (HIGH),
wildcard activation, extension-pack expansion, typosquat (MEDIUM).

Per-extension reuse of UNI/ENT/NET/TNT/MEM/SCR scanners with bounded
concurrency. Offline-first; --online opt-in. JetBrains discovery stubbed
for v1.1. 22 new tests (1296 total, was 1274).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

plugins/llm-security/tests/fixtures/ide-extensions/root-benign/extensions.json

@@ -0,0 +1,32 @@
+[
+  {
+    "identifier": { "id": "publisher.benign-ext" },
+    "version": "1.0.0",
+    "location": { "$mid": 1, "fsPath": "publisher.benign-ext-1.0.0", "path": "/publisher.benign-ext-1.0.0", "scheme": "file" },
+    "relativeLocation": "publisher.benign-ext-1.0.0",
+    "metadata": {
+      "installedTimestamp": 1700000000000,
+      "source": "gallery",
+      "id": "benign-ext",
+      "publisherId": "publisher",
+      "publisherDisplayName": "Publisher",
+      "isBuiltin": false,
+      "isApplicationScoped": false
+    }
+  },
+  {
+    "identifier": { "id": "theme.goodtheme" },
+    "version": "1.0.0",
+    "location": { "$mid": 1, "fsPath": "theme.goodtheme-1.0.0", "path": "/theme.goodtheme-1.0.0", "scheme": "file" },
+    "relativeLocation": "theme.goodtheme-1.0.0",
+    "metadata": {
+      "installedTimestamp": 1700000000000,
+      "source": "gallery",
+      "id": "goodtheme",
+      "publisherId": "theme",
+      "publisherDisplayName": "Theme",
+      "isBuiltin": false,
+      "isApplicationScoped": false
+    }
+  }
+]