Prefill: classify unknown cultivars into a reference group so the ledger still computes

The extraction schema gains cultivarGroup (typica/bourbon/ethiopian/
hybrid, classified by the LLM from coffee genetics); when the named
variety isn't in the cultivar table, deriveFields now falls back to the
group's first-crack anchor (number still comes only from the reference
table) instead of leaving 1.4 blank and breaking every downstream
calculation. deriveFields exported + unit-tested.

Co-Authored-By: Claude Fable 5 <[email protected]>

test/prefill-derive.test.js

@@ -0,0 +1,61 @@
+import test from "node:test";
+import assert from "node:assert/strict";
+import { deriveFields } from "../server/prefill.js";
+import { computeLedger } from "../shared/ledger.js";
+
+const base = {
+	coffeeName: "Test Coffee",
+	cultivar: null,
+	cultivarGroup: null,
+	origin: "Colombia",
+	producer: null,
+	process: "washed",
+	roastLevel: "light",
+	tastingNotes: [],
+	altitudeMasl: null,
+	screen: null,
+	moisturePct: null,
+	isBlend: false,
+	blendComponents: [],
+};
+
+test("known cultivar uses the cultivar table row", () => {
+	const { fields, provenance } = deriveFields({ ...base, cultivar: "Gesha" });
+	assert.equal(fields["1.1"], "Gesha");
+	assert.equal(fields["1.2"], "ethiopian");
+	assert.equal(fields["1.4"], "7:30");
+	assert.equal(provenance["1.4"], "cultivar-table");
+});
+
+test("unknown cultivar with a classified group falls back to the group anchor so the ledger computes", () => {
+	const { fields, provenance, warnings } = deriveFields({
+		...base,
+		cultivar: "Wush Wush",
+		cultivarGroup: "ethiopian",
+	});
+	assert.equal(fields["1.1"], "Wush Wush");
+	assert.equal(fields["1.2"], "ethiopian");
+	assert.equal(fields["1.4"], "7:25"); // midpoint of the ethiopian group anchor 7:20-7:30
+	assert.equal(provenance["1.4"], "group-table");
+	assert.match(warnings.join(" "), /group anchor/);
+	// The whole point: first crack is now computable
+	const ledger = computeLedger({ fields });
+	assert.equal(ledger.A !== null, true);
+});
+
+test("unknown cultivar in the unparseable hybrid group still degrades gracefully", () => {
+	const { fields, warnings } = deriveFields({
+		...base,
+		cultivar: "Mystery F1",
+		cultivarGroup: "hybrid", // group anchor is "follows parent" — not a number
+	});
+	assert.equal(fields["1.1"], "Mystery F1");
+	assert.equal(fields["1.4"], undefined);
+	assert.match(warnings.join(" "), /pick the nearest group by hand/);
+});
+
+test("unknown cultivar with no group keeps the old blank-fields warning", () => {
+	const { fields, warnings } = deriveFields({ ...base, cultivar: "Zebra SP" });
+	assert.equal(fields["1.4"], undefined);
+	assert.match(warnings.join(" "), /pick the nearest group by hand/);
+});