test(workbench): pure-helper coverage for toScene + pickActiveId

Adds 10 unit tests for the two helpers we hardened this session:

- toScene round-trips the core presentation fields and the two
  previously-dropped extras (viewingAsAgentId, scopeTagIds). Guards
  against the silent field-loss regression fixed in a1baf1053.
- pickActiveId covers empty lists, surviving current, MRU fallback,
  skipping deleted MRU entries, corrupted-JSON MRU payload, and
  non-string entries. Locks down the fallback ladder introduced in
  4e5c3179f so scenes[0] stays a last resort.

Both helpers are now exported from the .svelte.ts store. The test
file mocks `$app/environment.browser=true` and polyfills localStorage
so it runs without jsdom (the web app doesn't bundle jsdom as a test
dep).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/mana/apps/web/src/lib/stores/workbench-scenes.svelte.ts

@@ -87,7 +87,10 @@ function bumpMru(id: string) {
 	}
 }
 
-function toScene(local: LocalWorkbenchScene): WorkbenchScene {
+/** Exported for unit tests — converts a Dexie row to the public shape.
+ *  Regression guard: this previously dropped `viewingAsAgentId` and
+ *  `scopeTagIds`, silently breaking SceneAppBar's agent badge. */
+export function toScene(local: LocalWorkbenchScene): WorkbenchScene {
 	return {
 		id: local.id,
 		name: local.name,
@@ -119,7 +122,10 @@ async function ensureSeedScene(): Promise<string> {
 	return id;
 }
 
-function pickActiveId(scenes: WorkbenchScene[], current: string | null): string | null {
+/** Exported for unit tests — resolves the active scene id against the
+ *  available list, falling back to per-device MRU and finally to the
+ *  first sort-ordered scene. */
+export function pickActiveId(scenes: WorkbenchScene[], current: string | null): string | null {
 	if (scenes.length === 0) return null;
 	const ids = new Set(scenes.map((s) => s.id));
 	if (current && ids.has(current)) return current;

apps/mana/apps/web/src/lib/stores/workbench-scenes.test.ts

@@ -0,0 +1,159 @@
+/**
+ * Unit tests for the pure helpers in the workbench-scenes store.
+ *
+ * Covers the regressions fixed in a1baf1053 (toScene was silently
+ * dropping viewingAsAgentId + scopeTagIds) and 4e5c3179f (pickActiveId
+ * now consults the MRU stack instead of always returning scenes[0]).
+ *
+ * Only the pure exports are exercised — full integration tests against
+ * fake-indexeddb would also need to drive Svelte 5's $state through
+ * reactive updates, which isn't wired up for the store suite yet.
+ */
+
+import { beforeEach, describe, expect, it, vi } from 'vitest';
+
+// The store reads localStorage through `$app/environment.browser`, which
+// defaults to false under vitest/Node — that would short-circuit the MRU
+// fallback path we want to exercise. Pretending we're in the browser and
+// handing vi a minimal localStorage polyfill keeps the test environment
+// agnostic (no jsdom dependency).
+vi.mock('$app/environment', () => ({ browser: true }));
+
+if (typeof globalThis.localStorage === 'undefined') {
+	const backing = new Map<string, string>();
+	Object.defineProperty(globalThis, 'localStorage', {
+		configurable: true,
+		value: {
+			getItem: (k: string) => backing.get(k) ?? null,
+			setItem: (k: string, v: string) => void backing.set(k, String(v)),
+			removeItem: (k: string) => void backing.delete(k),
+			clear: () => backing.clear(),
+			key: (i: number) => Array.from(backing.keys())[i] ?? null,
+			get length() {
+				return backing.size;
+			},
+		},
+	});
+}
+
+import { toScene, pickActiveId } from './workbench-scenes.svelte';
+import type { LocalWorkbenchScene, WorkbenchScene } from '$lib/types/workbench-scenes';
+
+const MRU_LS_KEY = 'mana:workbench:sceneMru';
+
+function sceneFixture(overrides: Partial<WorkbenchScene> = {}): WorkbenchScene {
+	return {
+		id: 'scene-1',
+		name: 'Home',
+		description: null,
+		openApps: [{ appId: 'todo' }],
+		order: 0,
+		...overrides,
+	};
+}
+
+function localFixture(overrides: Partial<LocalWorkbenchScene> = {}): LocalWorkbenchScene {
+	return {
+		id: 'scene-1',
+		name: 'Home',
+		description: null,
+		openApps: [{ appId: 'todo' }],
+		order: 0,
+		createdAt: '2026-01-01T00:00:00.000Z',
+		updatedAt: '2026-01-01T00:00:00.000Z',
+		...overrides,
+	};
+}
+
+describe('toScene', () => {
+	it('copies the core presentation fields', () => {
+		const local = localFixture({
+			name: 'Deep Work',
+			description: 'Focus time',
+			openApps: [{ appId: 'todo' }, { appId: 'notes', maximized: true }],
+			order: 3,
+		});
+		const out = toScene(local);
+		expect(out).toMatchObject({
+			id: 'scene-1',
+			name: 'Deep Work',
+			description: 'Focus time',
+			order: 3,
+		});
+		expect(out.openApps).toHaveLength(2);
+		expect(out.openApps[1]).toEqual({ appId: 'notes', maximized: true });
+	});
+
+	it('preserves viewingAsAgentId and scopeTagIds', () => {
+		// Regression: these two were silently dropped, which broke the
+		// agent avatar pill in SceneAppBar and the auto-inferred scope
+		// in SceneHeader.
+		const local = localFixture({
+			viewingAsAgentId: 'agent-42',
+			scopeTagIds: ['tag-a', 'tag-b'],
+		});
+		const out = toScene(local);
+		expect(out.viewingAsAgentId).toBe('agent-42');
+		expect(out.scopeTagIds).toEqual(['tag-a', 'tag-b']);
+	});
+
+	it('tolerates absent optional fields', () => {
+		const local = localFixture({ description: undefined, openApps: undefined });
+		const out = toScene(local);
+		expect(out.description).toBeNull();
+		expect(out.openApps).toEqual([]);
+	});
+});
+
+describe('pickActiveId', () => {
+	beforeEach(() => {
+		localStorage.clear();
+	});
+
+	it('returns null when there are no scenes', () => {
+		expect(pickActiveId([], null)).toBeNull();
+		expect(pickActiveId([], 'missing')).toBeNull();
+	});
+
+	it('returns current when it is still in the list', () => {
+		const scenes = [sceneFixture({ id: 'a' }), sceneFixture({ id: 'b', order: 1 })];
+		expect(pickActiveId(scenes, 'b')).toBe('b');
+	});
+
+	it('falls back to scenes[0] when no current and no MRU', () => {
+		const scenes = [sceneFixture({ id: 'a' }), sceneFixture({ id: 'b', order: 1 })];
+		expect(pickActiveId(scenes, null)).toBe('a');
+	});
+
+	it('falls back to the newest MRU entry that still exists', () => {
+		// MRU stack with the most recent scene first.
+		localStorage.setItem(MRU_LS_KEY, JSON.stringify(['gone', 'b', 'a']));
+		const scenes = [sceneFixture({ id: 'a' }), sceneFixture({ id: 'b', order: 1 })];
+		// Current 'gone' is no longer available → skip; next MRU 'b' is available.
+		expect(pickActiveId(scenes, 'gone')).toBe('b');
+	});
+
+	it('skips MRU ids that were deleted and uses the next live one', () => {
+		localStorage.setItem(MRU_LS_KEY, JSON.stringify(['x', 'y', 'c']));
+		const scenes = [
+			sceneFixture({ id: 'a' }),
+			sceneFixture({ id: 'c', order: 1 }),
+			sceneFixture({ id: 'd', order: 2 }),
+		];
+		expect(pickActiveId(scenes, null)).toBe('c');
+	});
+
+	it('falls back to scenes[0] if MRU is corrupted', () => {
+		localStorage.setItem(MRU_LS_KEY, '{not-json');
+		const scenes = [sceneFixture({ id: 'a' }), sceneFixture({ id: 'b', order: 1 })];
+		expect(pickActiveId(scenes, null)).toBe('a');
+	});
+
+	it('ignores non-string entries in the MRU payload', () => {
+		// Simulate a future schema regression — any non-string entry
+		// should be dropped silently, not crash the fallback.
+		localStorage.setItem(MRU_LS_KEY, JSON.stringify(['a', 42, null, 'b']));
+		const scenes = [sceneFixture({ id: 'b' }), sceneFixture({ id: 'c', order: 1 })];
+		expect(pickActiveId(scenes, null)).toBe('b');
+	});
+});