Implement CE-WP-0005 T01-T08: demo app — sessions, uploads, ZIP archive

Turn the MVP into a self-contained demo. Users now:
  1. Land on an empty-state and create a named session.
  2. Drag-drop or pick arbitrary PDFs into that session.
  3. Annotate, build evidence, link to form fields — all session-scoped.
  4. Export the whole session as a single .zip archive (manifest +
     per-document PDFs).
  5. Import a .zip back — into a new session, or merged into an
     existing one (documents deduped by SHA-256 fingerprint;
     annotations/evidence/links added additively).

Architecture:
- New shared types: SessionId, Session, SessionArchiveManifest +
  parseSessionArchiveManifest with schema-version validation.
- SessionService (engine/services/sessions.ts) handles lifecycle
  (create/rename/delete/setActive) + emits 4 new events through its
  own bus; SharedContracts.md §4 lists the additions.
- SessionProvider (work/SessionContext.tsx) owns the cross-session
  state: service, per-session PdfByteStore registry, per-session
  version counter that drives EngineProvider remounts after imports.
- EngineProvider becomes session-aware (sessionId prop drives per-
  session localStorage keys). Bumping engineRevision after
  restoreFromStorage forces consumers to re-render so restored repos
  show up immediately.
- PdfByteStore (source/pdf/byte-store.ts) holds Uint8Array bytes per
  document and mints blob URLs; ingestPdfFromFile is the upload
  entry-point that wraps the existing ingestPdf pipeline.
- ADR-0008 locks the ZIP layout (manifest.json + documents/<id>.pdf),
  the manifest schema (schemaVersion 1), and the merge-on-collision
  policy. JSZip is the only new dependency.
- App.tsx restructured: SessionProvider at the root, EngineProvider
  keyed by ${sessionId}:${version}, hash routing #/s/<id>[/forms/demo],
  SessionMenu top-bar, CreateFirstSession empty state.
- New DocumentRemoved event for per-document delete cleanup in
  CollectionList; engine.documents.remove() is the new service method.

Tests:
- Unit: 16 SessionService lifecycle + persistence tests;
  per-session snapshot round-trip; PdfByteStore + ingestPdfFromFile;
  SessionArchive parser; exportSessionZip + importSessionZip with
  create + merge + corrupt-archive paths.
- DOM: UploadDropzone, session-scoped CollectionList delete,
  SessionMenu create/switch/rename, routing parser.
- E2E: tests/integration/session-export-reimport.dom.test.tsx walks
  the full create → annotate → export → reimport flow and asserts
  the additive merge (deduped doc + doubled evidence rows).
- Legacy E2Es updated to use a seed-session helper instead of the
  removed fixture-button flow.

Known limitation (documented in ADR-0008): re-importing your own
freshly-exported ZIP creates duplicate annotations. Forward pointer
left for an importBundleId follow-up.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

tests/integration/app-prd-scenario.dom.test.tsx

@@ -28,8 +28,6 @@ import userEvent from "@testing-library/user-event";
 import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
 
 import type { Selector } from "@shared/selector";
-import type { DocumentId, RepresentationId } from "@shared/ids";
-import type { Document, DocumentRepresentation } from "@shared/document";
 import type { PdfSelectionCapture } from "@anchor/index";
 import manifest from "../../fixtures/pdfs/manifest.json" with { type: "json" };
 
@@ -90,42 +88,8 @@ const SYNTHETIC_CANONICAL = [
   "Trailing prose that comes after the quote.",
 ].join(" ");
 
-vi.mock("@source/index", async (importOriginal) => {
-  const original = await importOriginal<typeof import("@source/index")>();
-  return {
-    ...original,
-    ingestPdf: vi.fn(async (_input: unknown, options?: { filename?: string }) => {
-      const documentId = ("doc_test_" + Math.random().toString(36).slice(2, 10)) as DocumentId;
-      const representationId = ("rep_test_" + Math.random().toString(36).slice(2, 10)) as RepresentationId;
-      const document: Document = {
-        id: documentId,
-        mediaType: "application/pdf",
-        ...(options?.filename ? { title: options.filename } : {}),
-        fingerprint: "synthetic-fingerprint-for-test",
-        createdAt: "2026-05-25T00:00:00.000Z",
-        updatedAt: "2026-05-25T00:00:00.000Z",
-      };
-      const representation: DocumentRepresentation = {
-        id: representationId,
-        documentId,
-        representationType: "pdf-text",
-        contentHash: "synthetic-fingerprint-for-test",
-        canonicalText: SYNTHETIC_CANONICAL,
-        pageMap: [{ page: 1, width: 595, height: 842 }],
-        offsetMap: [
-          {
-            page: 1,
-            globalStart: 0,
-            globalEnd: SYNTHETIC_CANONICAL.length,
-            pageLength: SYNTHETIC_CANONICAL.length,
-          },
-        ],
-        generatedAt: "2026-05-25T00:00:00.000Z",
-      };
-      return { document, representation };
-    }),
-  };
-});
+// CE-WP-0005: pre-seed a session with the fixture doc; no ingestPdf mock needed.
+import { seedSessionWithDoc, type SeedResult } from "./helpers/seed-session";
 
 // ---------------------------------------------------------------------------
 // Helpers
@@ -160,40 +124,40 @@ async function loadApp() {
 // ---------------------------------------------------------------------------
 
 describe("App — PRD scenario steps 1-8 (CE-WP-0002-T09)", () => {
+  let seeded: SeedResult;
+
   beforeEach(() => {
     resetViewerSnapshot();
     // Each test starts with empty localStorage.
     globalThis.localStorage?.clear();
-    // The fetch isn't reached (ingestPdf is mocked) — but stub it so that
-    // any accidental call returns gracefully instead of TypeError.
-    globalThis.fetch = vi.fn(async () =>
-      new Response(new Uint8Array([0x25, 0x50, 0x44, 0x46]).buffer, {
-        status: 200,
-        headers: { "Content-Type": "application/pdf" },
-      }),
-    );
+    if (typeof window !== "undefined") {
+      history.replaceState(null, "", window.location.pathname);
+    }
+    seeded = seedSessionWithDoc({
+      sessionName: "Demo",
+      documentTitle: FIXTURE.filename,
+      canonicalText: SYNTHETIC_CANONICAL,
+    });
   });
 
   afterEach(() => {
     vi.restoreAllMocks();
   });
 
-  it("walks the full slice-1 scenario: load → select → save → reload → click → scroll", async () => {
+  it("walks the full slice-1 scenario: load → select → save → reload → click → scroll", { timeout: 15000 }, async () => {
     const user = userEvent.setup();
 
-    // Step 1: open the app.
+    // Step 1: open the app. CE-WP-0005: a pre-seeded session boots
+    // straight into the active layout (no empty state).
     const { unmount } = await loadApp();
-    expect(screen.getByText("Collection")).toBeTruthy();
+    expect(screen.queryByTestId("empty-state")).toBeNull();
+    expect(screen.getByTestId("session-menu-toggle").textContent).toContain("Demo");
 
-    // Step 2: pick a fixture.
-    const fixtureButton = screen.getByRole("button", { name: new RegExp(FIXTURE.id) });
-    await user.click(fixtureButton);
-
-    // The mock viewer should have mounted with our test URL.
+    // Step 2: the fixture doc is pre-seeded into the active session, so
+    // the viewer mounts automatically — no fixture-button click needed.
     await waitFor(() => {
-      expect(viewerSnapshot.pdfUrl).toBeTruthy();
+      expect(viewerSnapshot.onSelectionCaptured).not.toBeNull();
     });
-    expect(decodeURIComponent(viewerSnapshot.pdfUrl!)).toContain(FIXTURE.filename);
 
     // Step 3: programmatically inject a selection for the known-good quote.
     expect(viewerSnapshot.onSelectionCaptured).not.toBeNull();
@@ -223,9 +187,11 @@ describe("App — PRD scenario steps 1-8 (CE-WP-0002-T09)", () => {
     });
     const savedAnnotationId = viewerSnapshot.storedAnnotationIds[0]!;
 
-    // Snapshot key from EngineContext.STORAGE_KEY — implementation detail
+    // Per-session snapshot key from CE-WP-0005 — implementation detail
     // but worth asserting once at the integration layer.
-    const stored = globalThis.localStorage?.getItem("citation-evidence:engine-snapshot:v1");
+    const stored = globalThis.localStorage?.getItem(
+      `citation-evidence:session:${seeded.sessionId}:engine-snapshot:v1`,
+    );
     expect(stored).toBeTruthy();
 
     // Step 6: reload — unmount and remount the App. The same localStorage is
@@ -237,9 +203,8 @@ describe("App — PRD scenario steps 1-8 (CE-WP-0002-T09)", () => {
     // The viewer should re-mount automatically because the active document
     // was persisted.
     await waitFor(() => {
-      expect(viewerSnapshot.pdfUrl).toBeTruthy();
+      expect(viewerSnapshot.onSelectionCaptured).not.toBeNull();
     });
-    expect(decodeURIComponent(viewerSnapshot.pdfUrl!)).toContain(FIXTURE.filename);
 
     // The sidebar should show the restored item.
     const restoredItem = await screen.findByText(/Important deadline clause/);