refactor: move broken fixtures into skill directory, remove global fixtures/

fixture: paths now resolve relative to skill's cases/ dir, not global.
Each validate skill keeps its broken fixtures locally.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

tests/skills/cases/meta-validate/error-bad-root.json

@@ -1,6 +1,6 @@
 {
   "name": "Валидатор находит ошибку: неверный корневой элемент",
-  "setup": "fixture:broken/catalog-bad-root",
+  "setup": "fixture:catalog-bad-root",
   "params": { "objectPath": "Catalogs/Bad.xml" },
   "expectError": true
 }

tests/skills/cases/meta-validate/fixtures/catalog-bad-root/Catalogs/Bad.xml

@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<WrongRoot xmlns="http://v8.1c.ru/8.3/MDClasses">
+  <Catalog uuid="00000000-0000-0000-0000-000000000001">
+  </Catalog>
+</WrongRoot>