Add SKILL.md for AI agent subtitle batch conversion reference

[baoyu0]

Summary

This PR adds a SKILL.md file to help AI coding agents (Claude Code, Hermes, Codex, etc.) work with Subtitle Edit's command-line interface for batch subtitle conversion and processing.

What's included

• Full CLI reference (/convert, /offset, /fps, /encoding, etc.)
• Common conversion examples (srt↔ass↔vtt, time offset, encoding)
• MKV extraction → conversion workflow (mkvtoolnix integration)
• Standalone subtitleedit-cli cross-platform tool reference
• Troubleshooting guide for common CLI issues
• Development build instructions

Why SKILL.md?

SKILL.md is an emerging standard (originally from Anthropic/Claude Code, now adopted across multiple AI coding tools) that provides structured instructions for AI agents. Having it in-repo means any AI agent working with the Subtitle Edit codebase will automatically understand how to use the CLI without needing external documentation lookups.

Related

• subtitleedit-cli: https://github.com/SubtitleEdit/subtitleedit-cli
• Agent skills ecosystem: https://github.com/obra/superpowers

[niksedk]

Thanks for putting this together, @baoyu0 — and sorry for the late call here.

We're going to close this one. A few reasons:

• The reference describes the GUI batch syntax (SubtitleEdit.exe /convert <pattern> <format>) and the separate subtitleedit-cli repo, but SE5 now ships a first-class CLI, seconv (in src/seconv), with different syntax (seconv <pattern> <format> --offset:… --fps:…), so the examples here would be misleading for agents.
• We've since added a canonical, maintained CLI reference at docs/reference/command-line.md (plus a short pointer in src/seconv/README.md and docs/features/seconv.md). A second standalone SKILL.md would duplicate that and drift out of sync — the exact problem we just consolidated away.
• File placement: a repo-root SKILL.md also sits oddly next to the existing .github/skills/ layout.

If you'd like to help here, a very welcome follow-up would be a small .github/skills/ entry for AI agents that simply points to docs/reference/command-line.md (single source of truth) rather than re-documenting the CLI. Thanks again!