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/forms-link-flow.dom.test.tsx

@@ -22,8 +22,7 @@ import { act, cleanup, render, screen, waitFor } from "@testing-library/react";
 import userEvent from "@testing-library/user-event";
 import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
 
-import type { Document, DocumentRepresentation } from "@shared/document";
-import type { AnnotationId, DocumentId, RepresentationId } from "@shared/ids";
+import type { AnnotationId } from "@shared/ids";
 import type { Selector } from "@shared/selector";
 
 import type { PdfSelectionCapture } from "@anchor/index";
@@ -55,38 +54,8 @@ vi.mock("@anchor/index", async (importOriginal) => {
 
 const FIXTURE = manifest.fixtures.find((f) => f.id === "fristsetzung-bezifferung")!;
 
-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 synthetic = "Synthetic canonical text for the form-link test.";
-      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,
-        pageMap: [{ page: 1, width: 595, height: 842 }],
-        offsetMap: [
-          { page: 1, globalStart: 0, globalEnd: synthetic.length, pageLength: synthetic.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 } from "./helpers/seed-session";
 
 async function loadApp() {
   const { App } = await import("@app/App");
@@ -96,12 +65,6 @@ async function loadApp() {
 describe("FormsApp — click-evidence-then-click-field linking (CE-WP-0003-T05)", () => {
   beforeEach(() => {
     globalThis.localStorage?.clear();
-    globalThis.fetch = vi.fn(async () =>
-      new Response(new Uint8Array([0x25, 0x50, 0x44, 0x46]).buffer, {
-        status: 200,
-        headers: { "Content-Type": "application/pdf" },
-      }),
-    );
     // Forms mode is hash-driven; make sure we start clean.
     if (typeof window !== "undefined") {
       history.replaceState(null, "", window.location.pathname);
@@ -114,17 +77,19 @@ describe("FormsApp — click-evidence-then-click-field linking (CE-WP-0003-T05)"
   });
 
   it("stages an evidence item then links it to the clicked field", async () => {
+    seedSessionWithDoc({
+      sessionName: "T05-link",
+      documentTitle: FIXTURE.filename,
+      canonicalText: "Synthetic canonical text for the form-link test.",
+    });
     const user = userEvent.setup();
     await loadApp();
 
     // Switch to Forms via the top-bar button.
     await user.click(screen.getByRole("button", { name: "Forms" }));
 
-    // The collection list is in the Forms layout too.
-    const fixtureBtn = screen.getByRole("button", { name: new RegExp(FIXTURE.id) });
-    await user.click(fixtureBtn);
-
-    // Wait for the fixture to load and the form to appear.
+    // CE-WP-0005: doc is pre-seeded into the active session.
+    // Wait for the form to appear.
     await waitFor(() => {
       expect(screen.queryByLabelText("Summary of the matter")).not.toBeNull();
     });
@@ -170,12 +135,12 @@ describe("FormsApp — click-evidence-then-click-field linking (CE-WP-0003-T05)"
     expect(screen.getByTestId("field-summary-chip").textContent).toMatch(/1 evidence/);
   });
 
-  it("starts in Review mode by default and switches to Forms via hash", async () => {
+  it("starts in the empty state when no session is active (CE-WP-0005 default)", async () => {
     await loadApp();
-    expect(screen.getByText("Collection")).toBeTruthy();
-    // Review pane's no-doc-open hint from EvidenceSidebar:
-    expect(screen.queryByText(/No document open/)).not.toBeNull();
-    // No demo form rendered yet
+    // The empty-state landing is what users see now until they create
+    // a session.
+    expect(screen.getByTestId("empty-state")).toBeTruthy();
+    // No demo form rendered yet.
     expect(screen.queryByText("Demo evidence-backed form")).toBeNull();
   });
 });