refactor(work-items): skills, references and evals name the binding in the convention home #11880

Problem

The work-items skills, references, eval scaffolds and adapters name .work-item-tracker.json.

Origin: Q551; ADR 0075 fix 11.

Fix

Point every work-items mention outside setup (K20) and the seam reader (K19) at
<home>/work-items.yaml; eval scaffolds write the YAML binding.

Done when

• git grep -l -F '.work-item-tracker' -- plugins/work-items ':!**/CHANGELOG.md' lists only the seam reader, its test and setup's migration files.
• python3 plugins/evals/skills/validate/scripts/validate-cases.py plugins/work-items/evals and bash plugins/skill-quality/scripts/check-skill.sh plugins/work-items/skills exit 0, and bash scripts/check-changelog-fragments.sh passes with a work-items fragment.

Parent: #7578