chore: import upstream snapshot with attribution

tests/unit/db-schema-columns-split.test.ts

@@ -0,0 +1,65 @@
+// Characterization of the db/core.ts schema-column split (god-file decomposition): the idempotent
+// ALTER-TABLE column reconcilers + table introspection helpers moved into db/schemaColumns.ts. These
+// run an in-memory SQLite db through the helpers to lock the observable behavior: ensure* adds missing
+// columns and is safe to re-run; hasTable/hasColumn/getTableColumns/quoteIdentifier introspect.
+import { test } from "node:test";
+import assert from "node:assert/strict";
+import { tryOpenSync } from "../../src/lib/db/adapters/driverFactory.ts";
+import {
+  ensureUsageHistoryColumns,
+  hasColumn,
+  hasTable,
+  quoteIdentifier,
+  getTableColumns,
+} from "../../src/lib/db/schemaColumns.ts";
+
+function openMemoryDb() {
+  // Synchronous in-memory adapter — no DATA_DIR / file handles to clean up.
+  const db = tryOpenSync(":memory:");
+  assert.ok(db, "expected a synchronous sqlite adapter for :memory:");
+  return db!;
+}
+
+test("quoteIdentifier escapes embedded double quotes", () => {
+  assert.equal(quoteIdentifier("plain"), '"plain"');
+  assert.equal(quoteIdentifier('we"ird'), '"we""ird"');
+});
+
+test("hasTable / hasColumn / getTableColumns introspect a live table", () => {
+  const db = openMemoryDb();
+  try {
+    db.exec("CREATE TABLE usage_history (id INTEGER PRIMARY KEY, model TEXT)");
+    assert.equal(hasTable(db, "usage_history"), true);
+    assert.equal(hasTable(db, "does_not_exist"), false);
+    assert.equal(hasColumn(db, "usage_history", "model"), true);
+    assert.equal(hasColumn(db, "usage_history", "nope"), false);
+    assert.deepEqual(getTableColumns(db, "usage_history").sort(), ["id", "model"]);
+  } finally {
+    db.close?.();
+  }
+});
+
+test("ensureUsageHistoryColumns adds missing columns and is idempotent", () => {
+  const db = openMemoryDb();
+  try {
+    db.exec("CREATE TABLE usage_history (id INTEGER PRIMARY KEY, model TEXT)");
+    assert.equal(hasColumn(db, "usage_history", "service_tier"), false);
+
+    ensureUsageHistoryColumns(db);
+    for (const col of [
+      "success",
+      "latency_ms",
+      "ttft_ms",
+      "error_code",
+      "service_tier",
+      "combo_strategy",
+    ]) {
+      assert.equal(hasColumn(db, "usage_history", col), true, `expected ${col} after ensure`);
+    }
+
+    // Re-running must not throw (columns already present) — idempotency.
+    assert.doesNotThrow(() => ensureUsageHistoryColumns(db));
+  } finally {
+    db.close?.();
+  }
+});