test(infra) AP scraper-pipeline integration tests

[jkeeley2073]

Summary

Backfill of the PR #41 family-wide test-infra template for the
ApGamePageScraper. AP is the closest sibling to CGC — both
multi-yield (.Game then .Link(s) per game), both HTML-index →
HTML-per-game with PDF link extraction — so the structure mirrors
CgcGamePageScraperTests tightly. The only material differences are
the discovery surface (XML sitemap vs HTML index page) and the
manufacturer-specific provenance values (SourceType.AmericanPinballGamePage,
"American Pinball Game Page", game_ap_{slug}, ap_games).

5 tests, +5 over the previous 430 = 435 total. Build clean,
zero warnings.

Tests added

1. ScrapeAsync_HappyPath_YieldsGameThenLinksWithProvenance — sitemap
   with 2 games, each with PDF/ZIP downloads. Asserts yield order
   (.Game, .Link(s), .Game, .Link(s) in sitemap order),
   .Link.GameSlug lineage to parent game, full provenance fields
   (SourceType, DiscoveryUrl, DiscoveryContext, ScrapedFrom,
   ScrapedAt, DiscoveredOn), and gate-vs-wire URL equality.
2. ScrapeAsync_PerPageFetchFailure_DoesNotAbortRun — one game page
   500s, the other two still yield. Politeness invariants hold under
   failure.
3. ScrapeAsync_DiscoveryFailure_AbortsThisSourceOnly — /sitemap.xml
   500s; scraper yields nothing and does not throw.
4. ScrapeAsync_PolitenessExceptionFromGate_PropagatesUp — gate
   throws on Acquire; exception propagates, no HTTP requests fire.
5. ScrapeAsync_GateThrowsOnReport_BubblesUp — symmetric Report-side
   throw also propagates.

Test plan

• dotnet test --filter ApGamePageScraperTests — 5/5 pass
• dotnet test — 435/435 pass (was 430)
• dotnet build -warnaserror — 0 warnings, 0 errors

Pre-push self-audit

/local-review deferred to the reviewer at merge time. 7-item
mechanical checklist:

1. Every option field is read. No new options added — uses
   existing ApOptions.BaseUrl. ✅
2. Sibling-diff for drift. Test file mirrors
   CgcGamePageScraperTests (same five test names, same assertion
   order, same helper-method shape). Manufacturer-specific values
   (slugs, source enum, discovery context, GameId prefix,
   DiscoveredOn token, sitemap content type) are the only
   intentional differences. ✅
3. No bare catch { }. Grep confirms zero matches in the new
   file. ✅
4. CLI / orchestrator wiring is end-to-end. No new scraper
   registered — this is a test-only change. AP scraper's CLI alias
   was wired in its original PR and the SourceAliasContractTests
   suite still passes. ✅
5. Tests assert behavior, not just structure. Happy-path asserts
   yield count, yield order, .Link.GameSlug lineage, full
   provenance fields, and gate-wire URL equality. Failure-isolation
   test asserts that 2 of 3 games still yield and that politeness
   invariants hold under failure. Discovery-failure test asserts
   empty result. Both PolitenessException tests assert the
   exception propagates and (in the Acquire case) that no HTTP
   requests fire. ✅
6. Build is zero-warning. dotnet build -warnaserror clean. ✅
7. Identity check. git log -1 --format='%an <%ae>' shows
   Jim Keeley <94459922+jkeeley2073@users.noreply.github.com>. ✅

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