gdown Agent Skills & AI Rules

## Changelog

Record user-facing changes as towncrier fragments, following
`changelog.d/README.md`; never edit `CHANGELOG.md` directly.

## Agent skills

### Issue tracker

Issues are tracked in GitHub Issues (github.com/wkentaro/gdown) via the `gh` CLI. See `docs/agents/issue-tracker.md`.

### Issue and pull request labels

Canonical issue types, triage roles, and pull-request verdicts are documented in `docs/agents/triage-labels.md`.

### Domain docs

Single-context: one `CONTEXT.md` + `docs/adr/` at the repo root. See `docs/agents/domain.md`.