fix(test): exclude .cache from Vitest discovery

Prevents vendored skill cache tests under .cache/praxstack-* from
polluting npm test when skills-and-personas integration runs locally.

Co-authored-by: Prax Lannister <praxstack@users.noreply.github.com>

Author: cursoragent

vitest.config.js

@@ -10,6 +10,7 @@ export default defineConfig({
       '**/.claude/skills/**',
       '**/.agents/skills/**',
       '**/.cursor/skills/**',
+      '**/.cache/**',
     ],
     coverage: {
       provider: 'v8',