feat(llm-security): /security ide-scan <url> — Marketplace/OpenVSX/direct VSIX (v6.4.0)

Pre-installation verification of VS Code extensions via URL — fetch a remote
VSIX, extract it in a hardened sandbox, and run the existing IDE scanner
pipeline against it. No npm dependencies.

Sources:
- VS Code Marketplace (publisher.gallery.vsassets.io direct download)
- OpenVSX (open-vsx.org official API)
- Direct .vsix HTTPS URLs

Defenses:
- HTTPS-only, TLS verified, manual redirect with per-source host whitelist
- 30s total timeout via AbortController
- 50MB compressed cap, 500MB uncompressed, 100x expansion ratio
- Zero-dep ZIP extractor: zip-slip, absolute paths, drive letters, NUL bytes,
  symlinks (Unix mode 0xA000), depth limits, ZIP64 rejected, encrypted rejected
- SHA-256 streamed during fetch, surfaced in meta.source
- Temp dir cleanup in all paths (try/finally)

Files:
- scanners/lib/vsix-fetch.mjs (HTTPS fetcher, host whitelist, streaming SHA-256)
- scanners/lib/zip-extract.mjs (zero-dep parser with hardening caps)
- knowledge/marketplace-api-notes.md (endpoint reference)
- 3 test files (48 tests added: vsix-fetch, zip-extract, ide-extension-url)

Tests: 1296 → 1344 (all green).

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

plugins/llm-security/bin/llm-security.mjs

@@ -26,9 +26,12 @@ Commands:
       Quick security posture assessment (16 categories)
   audit-bom <target> [--output-file <path>]
       Generate AI Bill of Materials (CycloneDX 1.6)
-  ide-scan [target] [--vscode-only] [--intellij-only] [--include-builtin]
+  ide-scan [target|url] [--vscode-only] [--intellij-only] [--include-builtin]
            [--online] [--format compact|json] [--fail-on <severity>]
-      Scan installed VS Code / JetBrains extensions (offline by default)
+      Scan installed VS Code / JetBrains extensions, OR fetch a remote VSIX:
+        - https://marketplace.visualstudio.com/items?itemName=publisher.name
+        - https://open-vsx.org/extension/publisher/name[/version]
+        - https://example.com/foo.vsix (direct .vsix download)
   benchmark [--adaptive] [--category <name>]
       Run attack simulation benchmark