docs(wiki): sync from /wiki @ 6880e79 (v3.0.0)
docs(wiki): full v2.0.1 rewrite (sync from main @ 9ab3644)
Add Tier 2 deep-dives (9 pages) Handle-Errors — Result<T>, IntegrationError, ErrorType, Match Configure-Resilience — what retries, backoff formula, circuit breaker Add-Validation — FluentValidation in pipeline, first-failure surfacing Cache-Query-Results — ICacheableQuery, success-only caching, key patterns Work-with-Dimensions — GetDimensionOrdersQuery, Builder, Reader Run-Smoke-Tests — both HTTP triggers, expected responses, CI usage Integrate-with-RELion — optional module, settings, custom queries Extend-the-Pipeline — custom commands, behaviours, direct IService use Test-with-TestKit — Result assertions, fakes, builders, test entities Replaces obsolete Write-Tests.md (subsumed by Test-with-TestKit.md).