feat(core): add sourceId to FeedItem (#72)

Each FeedSource implementation now sets sourceId on items
it produces, allowing consumers to trace items back to
their originating source.

Co-authored-by: Ona <no-reply@ona.com>

apps/aelis-backend/src/engine/http.test.ts

@@ -64,6 +64,7 @@ describe("GET /api/feed", () => {
 		const items: FeedItem[] = [
 			{
 				id: "item-1",
+				sourceId: "test",
 				type: "test",
 				priority: 0.8,
 				timestamp: new Date("2025-01-01T00:00:00.000Z"),
@@ -96,6 +97,7 @@ describe("GET /api/feed", () => {
 		const items: FeedItem[] = [
 			{
 				id: "fresh-1",
+				sourceId: "test",
 				type: "test",
 				priority: 0.5,
 				timestamp: new Date("2025-06-01T12:00:00.000Z"),

apps/aelis-backend/src/enhancement/merge.test.ts

@@ -9,6 +9,7 @@ import { mergeEnhancement } from "./merge.ts"
 function makeItem(overrides: Partial<FeedItem> = {}): FeedItem {
 	return {
 		id: "item-1",
+		sourceId: "test",
 		type: "test",
 		timestamp: new Date("2025-01-01T00:00:00Z"),
 		data: { value: 42 },

apps/aelis-backend/src/enhancement/merge.ts

@@ -2,6 +2,8 @@ import type { FeedItem } from "@aelis/core"
 
 import type { EnhancementResult } from "./schema.ts"
 
+const ENHANCEMENT_SOURCE_ID = "aelis.enhancement"
+
 /**
  * Merges an EnhancementResult into feed items.
  *
@@ -10,7 +12,11 @@ import type { EnhancementResult } from "./schema.ts"
  * - Returns a new array (no mutation)
  * - Ignores fills for items/slots that don't exist
  */
-export function mergeEnhancement(items: FeedItem[], result: EnhancementResult, currentTime: Date): FeedItem[] {
+export function mergeEnhancement(
+	items: FeedItem[],
+	result: EnhancementResult,
+	currentTime: Date,
+): FeedItem[] {
 	const merged = items.map((item) => {
 		const fills = result.slotFills[item.id]
 		if (!fills || !item.slots) return item
@@ -31,6 +37,7 @@ export function mergeEnhancement(items: FeedItem[], result: EnhancementResult, c
 	for (const synthetic of result.syntheticItems) {
 		merged.push({
 			id: synthetic.id,
+			sourceId: ENHANCEMENT_SOURCE_ID,
 			type: synthetic.type,
 			timestamp: currentTime,
 			data: { text: synthetic.text },

apps/aelis-backend/src/enhancement/prompt-builder.test.ts

@@ -7,6 +7,7 @@ import { buildPrompt, hasUnfilledSlots } from "./prompt-builder.ts"
 function makeItem(overrides: Partial<FeedItem> = {}): FeedItem {
 	return {
 		id: "item-1",
+		sourceId: "test",
 		type: "test",
 		timestamp: new Date("2025-01-01T00:00:00Z"),
 		data: { value: 42 },
@@ -60,7 +61,9 @@ describe("buildPrompt", () => {
 
 		expect(parsed.items).toHaveLength(1)
 		expect((parsed.items as Array<Record<string, unknown>>)[0]!.id).toBe("item-1")
-		expect((parsed.items as Array<Record<string, unknown>>)[0]!.slots).toEqual({ insight: "Weather insight" })
+		expect((parsed.items as Array<Record<string, unknown>>)[0]!.slots).toEqual({
+			insight: "Weather insight",
+		})
 		expect((parsed.items as Array<Record<string, unknown>>)[0]!.type).toBeUndefined()
 		expect(parsed.context).toHaveLength(0)
 	})

apps/aelis-backend/src/session/user-session.test.ts

@@ -76,6 +76,7 @@ describe("UserSession.feed", () => {
 		const items: FeedItem[] = [
 			{
 				id: "item-1",
+				sourceId: "test",
 				type: "test",
 				timestamp: new Date("2025-01-01T00:00:00.000Z"),
 				data: { value: 42 },
@@ -93,6 +94,7 @@ describe("UserSession.feed", () => {
 		const items: FeedItem[] = [
 			{
 				id: "item-1",
+				sourceId: "test",
 				type: "test",
 				timestamp: new Date("2025-01-01T00:00:00.000Z"),
 				data: { value: 42 },
@@ -113,6 +115,7 @@ describe("UserSession.feed", () => {
 		const items: FeedItem[] = [
 			{
 				id: "item-1",
+				sourceId: "test",
 				type: "test",
 				timestamp: new Date("2025-01-01T00:00:00.000Z"),
 				data: { value: 42 },
@@ -139,6 +142,7 @@ describe("UserSession.feed", () => {
 		let currentItems: FeedItem[] = [
 			{
 				id: "item-1",
+				sourceId: "test",
 				type: "test",
 				timestamp: new Date("2025-01-01T00:00:00.000Z"),
 				data: { version: 1 },
@@ -169,6 +173,7 @@ describe("UserSession.feed", () => {
 		currentItems = [
 			{
 				id: "item-1",
+				sourceId: "test",
 				type: "test",
 				timestamp: new Date("2025-01-02T00:00:00.000Z"),
 				data: { version: 2 },
@@ -190,6 +195,7 @@ describe("UserSession.feed", () => {
 		const items: FeedItem[] = [
 			{
 				id: "item-1",
+				sourceId: "test",
 				type: "test",
 				timestamp: new Date("2025-01-01T00:00:00.000Z"),
 				data: { value: 42 },