docs: add automated QA skill guide

[factory-nizar]

Summary

Adds a new guide documenting the /install-qa and qa skills -- how to set up automated end-to-end QA that tests your application as a real user would, with visual evidence, CI integration, and failure learning.

Where this page appears

• Docs > Features -- listed after Code Review in the main nav sidebar
• Guides > Skills -- added as the 9th skill in the cookbook (both EN and JP nav)
• Skills overview page (cli/configuration/skills) -- added to the numbered list and card grid

Files changed

• docs/guides/skills/automated-qa.mdx -- new guide (EN)
• docs/jp/guides/skills/automated-qa.mdx -- Japanese placeholder with summary
• docs/docs.json -- nav entries in Features group and Skills group (EN + JP)
• docs/cli/configuration/skills.mdx -- added to cookbook list and card grid

Content highlights

• Why automated QA matters
• Quick start with /install-qa
• What gets generated (orchestrator, sub-skills, config.yaml, workflow)
• Testing tools: agent-browser (web), tuistory (CLI/TUI), curl (API)
• CI integration with GitHub Actions
• Failure learning strategies
• Two real-world examples with actual QA reports:
  • CLI app (glow) -- Go TUI tested with tuistory
  • Full-stack web app (FastAPI + React) -- tested with agent-browser

closes FAC-18363

[factory-droid]

Droid finished @factory-nizar's task —— View job

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[factory-droid]

The new Automated QA guide looks solid and is correctly wired into EN nav. One concrete follow-up: the JP Docs sidebar “機能” (Features) group is missing the Automated QA entry even though the JP page exists, so JP users won’t find it from the Features section.