Add Playwright+Camoufox prerequisite checks to web-automation skill docs

skills/web-automation/claude-code/SKILL.md

@@ -21,7 +21,19 @@ pnpm install
 npx camoufox-js fetch
 ```
 
-If native dependency build errors appear (e.g., better-sqlite3), rebuild from the reported package directory.
+## Prerequisite Check (MANDATORY)
+
+Before running any automation, verify Playwright + Camoufox dependencies are installed and scripts are configured to use Camoufox.
+
+```bash
+cd ~/.claude/skills/web-automation/scripts
+node -e "require.resolve('playwright-core/package.json');require.resolve('camoufox-js/package.json');console.log('OK: playwright-core + camoufox-js installed')"
+node -e "const fs=require('fs');const t=fs.readFileSync('browse.ts','utf8');if(!/camoufox-js/.test(t)){throw new Error('browse.ts is not configured for Camoufox')}console.log('OK: Camoufox integration detected in browse.ts')"
+```
+
+If any check fails, stop and return:
+
+"Missing dependency/config: web-automation requires `playwright-core` + `camoufox-js` and Camoufox-based scripts. Run setup in this skill, then retry."
 
 ## Quick Reference