feat(19-02): add catalog-linked candidates, branched resolution, remove link/unlink routes

- getThreadWithCandidates LEFT JOINs globalItems with COALESCE for name, weight, price, image
- createCandidate accepts and stores globalItemId
- resolveThread branches: reference item (globalItemId set) vs standalone (full data copy)
- Removed link/unlink endpoints from items route (replaced by direct globalItemId FK)
- 6 new tests for catalog-linked candidates and branched resolution

tests/services/thread.service.test.ts

@@ -1,4 +1,6 @@
 import { beforeEach, describe, expect, it } from "bun:test";
+import { globalItems, items } from "../../src/db/schema.ts";
+import { eq } from "drizzle-orm";
 import {
 	createCandidate,
 	createThread,
@@ -616,6 +618,161 @@ describe("Thread Service", () => {
 		});
 	});
 
+	describe("catalog-linked candidates (globalItemId)", () => {
+		async function insertGlobalItem(
+			testDb: any,
+			data: {
+				brand: string;
+				model: string;
+				weightGrams?: number;
+				priceCents?: number;
+				imageUrl?: string;
+			},
+		) {
+			const [row] = await testDb
+				.insert(globalItems)
+				.values(data)
+				.returning();
+			return row;
+		}
+
+		it("createCandidate with globalItemId stores the value on the candidate row", async () => {
+			const gi = await insertGlobalItem(db, {
+				brand: "Big Agnes",
+				model: "Copper Spur HV UL2",
+				weightGrams: 1270,
+				priceCents: 44995,
+			});
+			const thread = await createThread(db, userId, {
+				name: "Tent Research",
+				categoryId: 1,
+			});
+			const candidate = await createCandidate(db, userId, thread.id, {
+				name: "placeholder",
+				categoryId: 1,
+				globalItemId: gi.id,
+			});
+
+			expect(candidate).toBeDefined();
+			expect(candidate.globalItemId).toBe(gi.id);
+		});
+
+		it("getThreadWithCandidates returns globalItemId field on each candidate", async () => {
+			const gi = await insertGlobalItem(db, {
+				brand: "MSR",
+				model: "Hubba Hubba",
+				weightGrams: 1540,
+			});
+			const thread = await createThread(db, userId, {
+				name: "Tent Options",
+				categoryId: 1,
+			});
+			await createCandidate(db, userId, thread.id, {
+				name: "placeholder",
+				categoryId: 1,
+				globalItemId: gi.id,
+			});
+
+			const result = await getThreadWithCandidates(db, userId, thread.id);
+			expect(result?.candidates).toHaveLength(1);
+			expect(result?.candidates[0].globalItemId).toBe(gi.id);
+		});
+
+		it("getThreadWithCandidates merges global item data for candidates with globalItemId", async () => {
+			const gi = await insertGlobalItem(db, {
+				brand: "Nemo",
+				model: "Tensor",
+				weightGrams: 425,
+				priceCents: 17995,
+			});
+			const thread = await createThread(db, userId, {
+				name: "Pad Research",
+				categoryId: 1,
+			});
+			await createCandidate(db, userId, thread.id, {
+				name: "placeholder",
+				categoryId: 1,
+				globalItemId: gi.id,
+			});
+
+			const result = await getThreadWithCandidates(db, userId, thread.id);
+			expect(result?.candidates[0].name).toBe("Nemo Tensor");
+			expect(result?.candidates[0].weightGrams).toBe(425);
+			expect(result?.candidates[0].priceCents).toBe(17995);
+		});
+
+		it("resolveThread with candidate having globalItemId creates a reference item", async () => {
+			const gi = await insertGlobalItem(db, {
+				brand: "Thermarest",
+				model: "NeoAir XLite",
+				weightGrams: 340,
+				priceCents: 20995,
+			});
+			const thread = await createThread(db, userId, {
+				name: "Pad Decision",
+				categoryId: 1,
+			});
+			const candidate = await createCandidate(db, userId, thread.id, {
+				name: "placeholder",
+				categoryId: 1,
+				globalItemId: gi.id,
+				notes: "Great pad",
+			});
+
+			const result = await resolveThread(db, userId, thread.id, candidate.id);
+			expect(result.success).toBe(true);
+			expect(result.item).toBeDefined();
+			expect(result.item?.globalItemId).toBe(gi.id);
+			expect(result.item?.name).toBe("Thermarest NeoAir XLite");
+			// Reference item should NOT copy weight/price from candidate
+			expect(result.item?.weightGrams).toBeNull();
+			expect(result.item?.priceCents).toBeNull();
+			expect(result.item?.notes).toBe("Great pad");
+		});
+
+		it("resolveThread with standalone candidate creates a full data copy item", async () => {
+			const thread = await createThread(db, userId, {
+				name: "Stove Decision",
+				categoryId: 1,
+			});
+			const candidate = await createCandidate(db, userId, thread.id, {
+				name: "Jetboil Flash",
+				categoryId: 1,
+				weightGrams: 371,
+				priceCents: 10995,
+				notes: "Fast boil",
+				productUrl: "https://example.com/jetboil",
+			});
+
+			const result = await resolveThread(db, userId, thread.id, candidate.id);
+			expect(result.success).toBe(true);
+			expect(result.item?.globalItemId).toBeNull();
+			expect(result.item?.name).toBe("Jetboil Flash");
+			expect(result.item?.weightGrams).toBe(371);
+			expect(result.item?.priceCents).toBe(10995);
+			expect(result.item?.productUrl).toBe("https://example.com/jetboil");
+		});
+
+		it("resolveThread reference item has brand+model as fallback name", async () => {
+			const gi = await insertGlobalItem(db, {
+				brand: "MSR",
+				model: "PocketRocket 2",
+			});
+			const thread = await createThread(db, userId, {
+				name: "Stove Research",
+				categoryId: 1,
+			});
+			const candidate = await createCandidate(db, userId, thread.id, {
+				name: "placeholder",
+				categoryId: 1,
+				globalItemId: gi.id,
+			});
+
+			const result = await resolveThread(db, userId, thread.id, candidate.id);
+			expect(result.item?.name).toBe("MSR PocketRocket 2");
+		});
+	});
+
 	describe("cross-user isolation", () => {
 		it("user cannot see other user's threads", async () => {
 			const userId2 = await createSecondTestUser(db);