EANCH-WP-0001 T02: bootstrap standalone TS package + test harness

Add package.json (name evidence-anchor, exports . and ./pdf, scripts
test/typecheck/lint), tsconfig.json (mirrors engine, DOM+jsx), vitest.config.ts
(happy-dom + react plugin), eslint.config.js (confines viewer libs to src/pdf/),
.nvmrc, and placeholder src entrypoints. Depends on @citation-evidence/engine
via sibling-checkout link only; no citation-evidence internals.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

vitest.config.ts

@@ -0,0 +1,17 @@
+import { defineConfig } from "vitest/config";
+import react from "@vitejs/plugin-react";
+
+// Pure selector/resolution tests are node-safe; the scroll/highlight and PDF
+// adapter tests touch the DOM, so the default environment is happy-dom. The
+// react plugin lets the PDF adapter (.tsx) compile under test.
+//
+// The one shared-type dependency, `@citation-evidence/engine`, resolves through
+// its package `exports` map (`./shared`) via the sibling-checkout link — no
+// local alias needed. Nothing here imports `citation-evidence` internals.
+export default defineConfig({
+  plugins: [react()],
+  test: {
+    environment: "happy-dom",
+    globals: false,
+  },
+});