[codex] Add HSK Anki deck artifacts

[Hol-ick]

Summary

• Add HSK 1-3 Anki deck artifacts under decks/hsk-anki-deck/
• Include final import-ready txt, APKG export, generation scripts, and source Anki exports
• Exclude the copyrighted source PDF from Git tracking

Validation

• Verified final import txt has 600 data rows
• Verified final import txt has 10 columns per row: 9 note fields plus row-level tag column

Notes

• This PR intentionally stages only the new HSK deck artifact folder and does not include the existing unrelated local DeckHub working-tree changes.