feat(backend): wire feed renderers into API

Add FeedRenderer and FeedRendererProvider to support server-side
rendering of feed items via ?render=json-render query param.

- FeedRenderer maps sourceId to FeedItemRenderer, renders matching
  items and drops the rest
- FeedRendererProvider mirrors FeedSourceProvider pattern for
  per-user renderer construction
- UserSession exposes renderer, handler converts JrxNode to Spec
- Returns 400 for unknown render format, 500 if renderer missing

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

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

@@ -1,10 +1,19 @@
-import type { ActionDefinition, ContextEntry, FeedItem, FeedSource } from "@aelis/core"
+import type {
+	ActionDefinition,
+	ContextEntry,
+	FeedItem,
+	FeedItemRenderer,
+	FeedSource,
+} from "@aelis/core"
+import type { Spec } from "@json-render/core"
 
 import { contextKey } from "@aelis/core"
+import { JRX_NODE } from "@nym.sh/jrx"
 import { describe, expect, test } from "bun:test"
 import { Hono } from "hono"
 
 import { mockAuthSessionMiddleware } from "../auth/session-middleware.ts"
+import { FeedRenderer } from "../session/feed-renderer.ts"
 import { UserSessionManager } from "../session/index.ts"
 import { registerFeedHttpHandlers } from "./http.ts"
 
@@ -19,6 +28,17 @@ interface FeedResponse {
 	errors: Array<{ sourceId: string; error: string }>
 }
 
+interface RenderedFeedResponse {
+	items: Array<{
+		id: string
+		type: string
+		timestamp: string
+		data: Record<string, unknown>
+		ui: Spec
+	}>
+	errors: Array<{ sourceId: string; error: string }>
+}
+
 function createStubSource(
 	id: string,
 	items: FeedItem[] = [],
@@ -150,6 +170,168 @@ describe("GET /api/feed", () => {
 	})
 })
 
+describe("GET /api/feed?render=json-render", () => {
+	const stubRenderer: FeedItemRenderer = (item) => ({
+		$$typeof: JRX_NODE,
+		type: "FeedCard",
+		props: {},
+		children: [
+			{
+				$$typeof: JRX_NODE,
+				type: "SansSerifText",
+				props: { content: `Rendered: ${item.data.value}` },
+				children: [],
+				key: undefined,
+				visible: undefined,
+				on: undefined,
+				repeat: undefined,
+				watch: undefined,
+			},
+		],
+		key: undefined,
+		visible: undefined,
+		on: undefined,
+		repeat: undefined,
+		watch: undefined,
+	})
+
+	const rendererProvider = {
+		feedRendererForUser: () => new FeedRenderer({ "test-source": stubRenderer }),
+	}
+
+	test("returns rendered items with ui field as Spec", async () => {
+		const items: FeedItem[] = [
+			{
+				id: "item-1",
+				sourceId: "test-source",
+				type: "renderable",
+				timestamp: new Date("2025-01-01T00:00:00.000Z"),
+				data: { value: "hello" },
+			},
+		]
+		const manager = new UserSessionManager({
+			providers: [() => createStubSource("test", items)],
+			rendererProvider,
+		})
+		const app = buildTestApp(manager, "user-1")
+
+		const res = await app.request("/api/feed?render=json-render")
+
+		expect(res.status).toBe(200)
+		const body = (await res.json()) as RenderedFeedResponse
+		expect(body.items).toHaveLength(1)
+		expect(body.items[0]!.id).toBe("item-1")
+		expect(body.items[0]!.ui).toBeDefined()
+		expect(body.items[0]!.ui.root).toBeDefined()
+		expect(body.items[0]!.ui.elements).toBeDefined()
+	})
+
+	test("drops items without a renderer", async () => {
+		const items: FeedItem[] = [
+			{
+				id: "renderable-1",
+				sourceId: "test-source",
+				type: "renderable",
+				timestamp: new Date("2025-01-01T00:00:00.000Z"),
+				data: { value: "yes" },
+			},
+			{
+				id: "unrenderable-1",
+				sourceId: "other-source",
+				type: "no-renderer",
+				timestamp: new Date("2025-01-01T00:00:00.000Z"),
+				data: { value: "no" },
+			},
+		]
+		const manager = new UserSessionManager({
+			providers: [() => createStubSource("test", items)],
+			rendererProvider,
+		})
+		const app = buildTestApp(manager, "user-1")
+
+		const res = await app.request("/api/feed?render=json-render")
+
+		expect(res.status).toBe(200)
+		const body = (await res.json()) as RenderedFeedResponse
+		expect(body.items).toHaveLength(1)
+		expect(body.items[0]!.id).toBe("renderable-1")
+	})
+
+	test("returns empty items when no renderers match", async () => {
+		const items: FeedItem[] = [
+			{
+				id: "item-1",
+				sourceId: "other-source",
+				type: "no-renderer",
+				timestamp: new Date("2025-01-01T00:00:00.000Z"),
+				data: { value: 42 },
+			},
+		]
+		const manager = new UserSessionManager({
+			providers: [() => createStubSource("test", items)],
+			rendererProvider,
+		})
+		const app = buildTestApp(manager, "user-1")
+
+		const res = await app.request("/api/feed?render=json-render")
+
+		expect(res.status).toBe(200)
+		const body = (await res.json()) as RenderedFeedResponse
+		expect(body.items).toHaveLength(0)
+	})
+
+	test("returns 400 for unknown render format", async () => {
+		const manager = new UserSessionManager({
+			providers: [() => createStubSource("test")],
+			rendererProvider,
+		})
+		const app = buildTestApp(manager, "user-1")
+
+		const res = await app.request("/api/feed?render=unknown")
+
+		expect(res.status).toBe(400)
+		const body = (await res.json()) as { error: string }
+		expect(body.error).toContain("unknown")
+	})
+
+	test("returns 500 when renderer is not available", async () => {
+		const manager = new UserSessionManager({
+			providers: [() => createStubSource("test")],
+		})
+		const app = buildTestApp(manager, "user-1")
+
+		const res = await app.request("/api/feed?render=json-render")
+
+		expect(res.status).toBe(500)
+		const body = (await res.json()) as { error: string }
+		expect(body.error).toContain("not available")
+	})
+
+	test("without render param returns raw items (no ui field)", async () => {
+		const items: FeedItem[] = [
+			{
+				id: "item-1",
+				sourceId: "test-source",
+				type: "renderable",
+				timestamp: new Date("2025-01-01T00:00:00.000Z"),
+				data: { value: 42 },
+			},
+		]
+		const manager = new UserSessionManager({
+			providers: [() => createStubSource("test", items)],
+			rendererProvider,
+		})
+		const app = buildTestApp(manager, "user-1")
+
+		const res = await app.request("/api/feed")
+
+		expect(res.status).toBe(200)
+		const body = (await res.json()) as FeedResponse
+		expect(body.items).toHaveLength(1)
+		expect(body.items[0]!).not.toHaveProperty("ui")
+	})
+})
+
 describe("GET /api/context", () => {
 	const weatherKey = contextKey("aelis.weather", "weather")
 	const weatherData = { temperature: 20, condition: "Clear" }