test(infra) JJP scraper-pipeline integration tests

[jkeeley2073]

Summary

Backfill of the PR #41 family-wide scraper-pipeline test-infra template against JjpProductScraper. JJP is a single-yield scraper (.Game only) on a Shopify storefront. Discovery is the canonical Shopify pattern: fetch /collections/{slug}/products.json for the pinball-machine handle set, walk the sitemap index for product sub-sitemaps, filter the listed product URLs against the handle set, then fetch each filtered product page and yield. The five tests use the shared FakePolitenessGate + QueueingHttpMessageHandler from PR #41 to pin behaviors the unit-test surface couldn't reach: yield order, provenance-field propagation onto ScrapedItem, SourceType.JjpProductPage and "JJP Product Page" discovery context, gate-vs-wire URL byte-equality, per-page failure isolation, discovery failure aborting only this source, and PolitenessException propagation on both Acquire and Report paths.

Touches only the new test file plus a single CHANGELOG bullet inserted directly after the family-wide test-infra entry. No production code changed; no JjpProductScraper bugs found in the test path. (Note: the two pre-existing JJP drift items surfaced by /local-review of PR #43 — ExtractSlug null-guard and NormalizeAvailability visibility — are intentionally out of scope for this test-infra PR and tracked separately.)

Test Plan

• dotnet build -nologo -v:m → 0 warnings, 0 errors
• dotnet test --filter "FullyQualifiedName~JjpProductScraperTests" → 5/5 pass (878 ms)
• dotnet test (full suite) → 435/435 pass (was 430 on main; +5 = the new tests)

Tests added (all in tests/PinballWizard.Scraper.Tests/Scraping/Jjp/JjpProductScraperTests.cs):

• ScrapeAsync_HappyPath_YieldsGamesInListOrderWithProvenance — 3 fixtured products surface from the collection JSON + sitemap walk; assert .Game yield order matches sitemap order, SourceType.JjpProductPage, "JJP Product Page" context, DiscoveryUrl per item, Source.ScrapedFrom = product URL, Source.ScrapedAt non-default, DiscoveredOn contains "jjp_products", every wire URL byte-equals every gate-acquired and gate-reported URL.
• ScrapeAsync_PerPageFetchFailure_DoesNotAbortRun — middle product page returns 500; the other two still yield; the 500 is reported to the gate.
• ScrapeAsync_DiscoveryFailure_AbortsThisSourceOnly — /collections/pinball-machines-for-sale/products.json returns 500; scraper yields nothing without throwing.
• ScrapeAsync_PolitenessExceptionFromGate_PropagatesUp — gate.ThrowOnAcquire set; assert PolitenessException propagates and zero wire requests fired.
• ScrapeAsync_GateThrowsOnReport_BubblesUp — gate.ThrowOnReport set; assert PolitenessException propagates from the first response report (collection JSON fetch).

Out of Scope

• The two pre-existing JJP drift items from PR refactor(multimorphic) adopt shared JsonLdProductParser #43's /local-review (ExtractSlug null-guard, NormalizeAvailability visibility) — tracked separately.
• Family backfill for the other six scrapers (PB / BoF / Multimorphic / AP / Spooky / Stern.Manuals) — running in parallel worktrees.
• Any production-code changes; this PR is test-only.

Checklist

• CI is green (build + test + coverage + CodeQL + sanitization)
• PR title follows the Conventional Commits format above
• If this is a new architectural decision, an ADR has been added under docs/adr/ — N/A, test-only
• If user-visible behavior changes, README.md and/or docs/ are updated in the same PR — N/A, no behavior change
• If a memory in ~/.claude/projects/c--projects-PinballWizard/memory/ is now stale, it has been updated or removed in the same PR — N/A
• No TODO / FIXME / commented-out code committed
• No new entries in <NoWarn> without a comment explaining why and the removal criterion

Pre-push self-audit (additive PRs)

Step 0 — /local-review (qualitative)

• Ran /local-review and addressed every 🔴 finding before push
• Local review outcome: deferred to human reviewer at merge time per the parallel-backfill task spec — six sibling backfill PRs are queued and the reviewer will run /local-review once across the family-merge sequence to catch any cross-PR drift.

Step 1 — Mechanical checklist

• Every new *Options property has at least one real getter call in src/ — N/A, no production code added
• Sibling-diffed against the closest existing implementation (CgcGamePageScraperTests); drift is justified — JJP-specific deltas: discovery is collection JSON + sitemap walk vs. menu HTML; single-yield (.Game only) vs. mixed yields; provenance asserts DiscoveryUrl equals product page URL because there is no separate index discovery URL on the per-yield path
• No bare catch { } — none added (only Assert.ThrowsAsync<PolitenessException> for the propagation tests)
• New ISourceScraper? — N/A, test-only PR
• Tests assert behavior, not just structure — every test name maps to a fixture that triggers the named condition (a 500 on the middle page, a 500 on the discovery endpoint, gate.ThrowOnAcquire / ThrowOnReport)
• Build is zero-warning — confirmed via dotnet build -nologo -v:m
• git log -1 --format='%an <%ae>' shows personal noreply, not work email — verified: Jim Keeley <94459922+jkeeley2073@users.noreply.github.com>