v4.0.0

4.0.0: TCGplayer total_asc/total_desc sorts, drop sale_count (#12)

* 4.0.0: TCGplayer total_asc/total_desc sorts, drop sale_count

TcgplayerSort gains total_asc and total_desc, which the API now accepts on
both TCGplayer listings endpoints: they order by price + shipping_price, the
order TCGplayer's own site uses, where price_asc orders by item price alone.

PriceHistoryPoint loses sale_count. The API removed it: it counted our daily
price snapshots (normally 1) and was being read as sales volume. Removing a
field from a public interface is the major bump.

Verified with npm run typecheck and npm run build.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TzmZo2tRyS2mzKWeLtSDiu

* Catch up on API fields the SDK never learned

An audit of every public response struct and query parameter against the
SDK types found four gaps, all older than this release:

- docs_url on error bodies was parsed away. It is now docsUrl on every
  PkmnPricesError, null when there was no body to read it from.
- grade_qualifier on eBay comps: Pristine and Black Label tens carry the
  same grade as a plain ten and sell well above it.
- condition and variant filters on price history.
- grader filter on the card list, beside the grade filter it already had.

Verified with npm run typecheck and npm run build.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TzmZo2tRyS2mzKWeLtSDiu

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Co-authored-by: Claude Fable 5.1 <noreply@anthropic.com>