docs/providers/NEW_PROVIDER.md items the PR had not reached yet, plus the two
surfaces that are functional rather than cosmetic:
- docs/providers/dsh.md and its row in the provider index, documenting the
storage layout, the JSONL-backend-only scope (the opt-in SQLite persistence
backend is not read), and that DSH is a developer preview whose format
version 0 implies no compatibility.
- CHANGELOG entry under Unreleased.
- README provider count 40 -> 41 and a data-locations row.
- app/package.json: $HOME/.dsh in the snap personal-files allowlist, without
which the Linux snap build cannot read DSH sessions at all.
- UsageDataChangeGuard: the DSH sessions root, without which the menubar never
notices a new session and does not refresh.
- Bumps the dsh parse version, since the parser's attribution changed.
