diigo-cache: SQL in .sql files, behind a read-only facet

No SQL text in the cache logic any more. Statements live in two files,
parsed by sqlStatements (`-- name:` sections, as in finquick's
brcal/gcbook.js) and imported as text (wrangler Text rule for *.sql):

- cache-read.sql: selects only, checked when the module loads
- cache-write.sql: schema, the v2 renumbering, etch, drops

store.ts turns them into two frozen facets with domain methods:
makeReader(sql) runs only the read statements (page, knownTotal,
deepestPageSince, pagesThrough); makeWriter(storage) only the write
ones (migrate, etch, dropPagesThrough), each change one transaction.

The cache migrates in its constructor under blockConcurrencyWhile, as
Cloudflare recommends, so readers never meet missing tables; the
migration test plants v1 storage and evicts to get a fresh activation.
A viewer() facet (PageViewer: stored pages and fill progress, from the
reader alone) is added for the public page.

Pure refactor: stored state and behavior unchanged.

Generated-by: Claude Opus 5.5

diigo-cache/tests/caches.test.ts

@@ -133,19 +133,18 @@ describe("page numbering (schema v2)", () => {
 	it("migrates v1 storage: a stored 'page n' was really page n+1, so it is renumbered, not refetched", async () => {
 		const stub = testEnv.CACHE_DO.get(testEnv.CACHE_DO.newUniqueId());
 		await stub.setup({ webappId: WEBAPP_ID });
-		// the shape v1 left: tables, a page 1 holding what diigo's
-		// page_num=1 returned (really page 2), and no schema marker
+		// the shape v1 left: a page 1 holding what diigo's page_num=1
+		// returned (really page 2), and no schema marker; then a fresh
+		// activation, whose constructor migrates
 		await runInDurableObject(stub, (_obj, state) => {
 			const sql = state.storage.sql;
-			sql.exec(`create table items (item_id text primary key, url text not null, title text not null,
-				private integer not null, json text not null, updated text not null)`);
-			sql.exec("create table pages (page_num integer primary key, count integer not null, total integer, etched_at text not null)");
-			sql.exec("create table page_members (page_num integer not null, pos integer not null, item_id text not null, primary key (page_num, pos))");
 			sql.exec("insert into items values ('a', 'https://a.example/', 'old page one, first', 0, '{\"title\":\"A\"}', '1')");
 			sql.exec("insert into items values ('b', 'https://b.example/', 'old page one, second', 0, '{\"title\":\"B\"}', '1')");
 			sql.exec("insert into pages values (1, 100, 250, '2026-10-07T00:00:00.000Z')");
 			sql.exec("insert into page_members values (1, 1, 'a'), (1, 2, 'b')");
+			state.storage.kv.delete("schema");
 		});
+		await evictDurableObject(stub);
 		const before = await testEnv.WEBAPP.calls();
 		const two = await stub.page(2, PAGE_SIZE);
 		expect(two.cached).toBe(true);