Fix: vendor static-HTML parsers so skill installs detect fully (#434)

Skill and plugin copies of the detector had no htmlparser2/css-select/css-tree/domutils, so HTML scans silently fell back to regex and exited 0. Bundle those parsers into the engine tree and exit 1 if the fallback still fires.

AI assistance: Cursor Grok 4.6 implemented this change.

Co-authored-by: Cursor <cursoragent@cursor.com>

scripts/lib/static-html-parsers.entry.mjs

@@ -0,0 +1,6 @@
+export * as htmlparser2 from 'htmlparser2';
+export * as cssSelect from 'css-select';
+export * as domutils from 'domutils';
+import parse from 'css-tree/parser';
+import generate from 'css-tree/generator';
+export const csstree = { parse, generate };