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>

eslint.config.js

@@ -0,0 +1,49 @@
+// ESLint flat config — keeps viewer-library imports behind the PDF adapter
+// boundary and the selector/resolution core pure.
+
+import js from "@eslint/js";
+import tseslint from "typescript-eslint";
+import importPlugin from "eslint-plugin-import";
+import globals from "globals";
+
+const VIEWER_LIBS = ["pdfjs-dist", "react", "react-dom", "react-pdf-highlighter-plus"];
+
+export default tseslint.config(
+  {
+    ignores: ["dist/", "node_modules/", "coverage/", "**/*.d.ts"],
+  },
+  js.configs.recommended,
+  ...tseslint.configs.recommended,
+  {
+    files: ["src/**/*.{ts,tsx}"],
+    languageOptions: {
+      ecmaVersion: 2022,
+      sourceType: "module",
+      globals: { ...globals.node, ...globals.browser },
+    },
+    plugins: {
+      import: importPlugin,
+    },
+    settings: {
+      "import/resolver": {
+        typescript: { project: "./tsconfig.json" },
+      },
+    },
+  },
+  {
+    // The pure core (selectors, resolution, highlight helpers) must not pull in
+    // any concrete viewer library — those live only under src/pdf/.
+    files: ["src/selectors/**/*.ts", "src/highlight/**/*.ts", "src/types.ts"],
+    rules: {
+      "no-restricted-imports": [
+        "error",
+        {
+          paths: VIEWER_LIBS.map((name) => ({
+            name,
+            message: "Viewer libraries are confined to src/pdf/ (adapter boundary).",
+          })),
+        },
+      ],
+    },
+  },
+);