Add a repository conformance suite

AGENTS.md

@@ -79,7 +79,9 @@ The WebView root component is assigned to `globalThis.webViewComponent` (not exp
 
 Drafts are loaded and saved through [AnalysisRepository](src/types/analysis-repository.ts), the seam a later storage backend implements. [DraftRepository](src/services/draftRepository.ts) implements it over the draft envelope and its per-book shards, and rewrites only the books that changed. It imports nothing from PAPI and reaches storage only through a `KeyValueStorage`. That lets the perf harness run it in Node, straight over the storage files ([perf/storage.ts](perf/storage.ts)).
 
-Saved projects are listed through [ProjectSummaries](src/services/projectSummaries.ts): one record holding every project's summary, rewritten on each project write so listing reads no analysis. It is PAPI-free in the same way.
+[The conformance suite](src/__tests__/analysis-repository-conformance.ts) defines the seam: every `AnalysisRepository` implementation must pass it, and [draftRepository.conformance.test.ts](src/__tests__/services/draftRepository.conformance.test.ts) runs it against `DraftRepository`. A behavior every implementation owes goes in the suite; one particular to an implementation, such as which shards a save rewrites, goes in that implementation's own tests. A later backend runs the suite by passing `describeAnalysisRepositoryConformance` a factory that returns a fresh `ConformanceStore` for each test.
+
+Saved projects are listed through [ProjectSummaries](src/services/projectSummaries.ts): one record holding every project's summary, rewritten on each project write so listing reads no analysis. Like `DraftRepository`, it is PAPI-free.
 
 ### Components