i18n: add Thai (th) to automated docs translation workflow

## Summary Requesting Thai (`th`) be added to the automated docs translation workflow, alongside the existing locales (`ar`, `de`, `es`, `fr`, `id`, `it`, `ja-jp`, `ko`, `pl`, `pt-br`, `tr`, `uk`, `zh-cn`). Since the recent refactor to `translate-locale-reusable.yml`, adding a new locale should be a small config change. ## Proposed locale code `th` — Thai has effectively one written locale in practical use, so a region suffix isn't needed. This matches the style of `ar`, `de`, `ko`, etc. ## Why Thai developers are currently underserved by the docs, and the new GPT-5.4 auto-translation path makes adding a new locale low-cost. ## Feedback process Following the same pattern as the Chinese thread in openclaw/openclaw#6995, once Thai output exists it would be useful to have a parallel tracking issue on `openclaw/openclaw` for Thai translation feedback, so the split stays consistent: - **Source doc bugs** → reported on `openclaw/openclaw` (this `docs` repo is a copy + translation target, not where source fixes land) - **Thai translation output bugs** → Thai equivalent tracking issue on `openclaw/openclaw` Could a maintainer confirm the preferred process for spinning up the Thai tracking issue when the time comes? Happy to open it myself and link it back here if that's the expected flow. ## Offer to help I work on Thai NLP (PyThaiNLP contributor) and can help review sample translation output once the workflow runs, and report systematic issues in the tracking thread.