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-mixed/pack.big-1.0.0/package.json

@@ -0,0 +1,15 @@
+{
+  "publisher": "pack",
+  "name": "big",
+  "version": "1.0.0",
+  "displayName": "Big Pack",
+  "description": "Installs several other extensions",
+  "engines": { "vscode": "^1.80.0" },
+  "categories": ["Extension Packs"],
+  "extensionPack": [
+    "alpha.one",
+    "beta.two",
+    "gamma.three",
+    "delta.four"
+  ]
+}