C02: P1: catalog and price adapters

Go implementation tracking epic

Selected stack: Go + Wails v2 + React/TypeScript + SQLite. Implementation starts on the next machine. Each child below is a separate PR; do not implement this epic in one PR.

Child tasks

• C02a: Catalog ingestion and atomic sync
  • Merged prerequisites: C01b.
  • Acceptance: R2: catalog adapter stages/validates/promotes; malformed/partial/offline sync retains last valid revision; source and freshness persisted.
• C02b: Cached catalog search screen
  • Merged prerequisites: C02a.
  • Acceptance: R2/R8: search, loading/empty/stale/retry states and keyboard focus; measure 10,000-item cached search against budget.
• C02c: Market quote service
  • Merged prerequisites: C01b, F03b.
  • Acceptance: R3: platform/rank/price-type keys, request deduplication, central rate limiting and stale cache; timeout/429/malformed fixture tests.
• C02d: Price details in catalog
  • Merged prerequisites: C02b, C02c.
  • Acceptance: R3/R8: timestamp/type/volume shown, unavailable distinct from zero; offline UI demonstration and readable scale checks.

Workflow

See TASKS.md, ROADMAP.md, and CONTRIBUTING.md. Aim for 100-400 handwritten changed lines per PR; split above 600 unless inseparable. Merge prerequisites before dependents. Update task evidence and this checklist after each completed PR. Close this epic only when every child passes; optional work can remain deferred.

All tasks are not started. Live game access and publication/merge actions follow the user's explicit authorization. The planning handoff does not claim runtime validation.

Read TASKS.md, ROADMAP.md, and CONTRIBUTING.md, then review the four child-task acceptance lists and their prerequisites. This is a planning epic rather than a single change, so work should begin with an individual child PR. Done means every child passes its stated acceptance checks and the checklist and task evidence are updated.