Fix typo in OpenFastTrace skill reference URL

[kaklakariada]

The OpenFastTrace spec-driven-development workflow references:

https://raw.githubusercontent.com/itsallcode/openfasttrace/refs/heads/main/.agends/skills/openfasttrace/SKILL.md

The .agends path is misspelled and returns 404. The repository tree contains the canonical skill at:

https://raw.githubusercontent.com/itsallcode/openfasttrace/refs/heads/main/.agents/skills/openfasttrace/SKILL.md

Please replace the broken URL in .agents/skills/openfasttrace-spec-driven-development/SKILL.md.