Implement CE-WP-0009: wire umbrella to @citation-evidence/engine

Add link: dependency on citation-engine, retarget @shared/@engine aliases,
remove in-repo shared/engine copies. ADR-0002 accepted (option B).
172 tests, typecheck, and lint pass.

eslint.config.js

@@ -1,23 +1,28 @@
 // ESLint flat config (ESLint 9+).
 // Enforces the partition dependency map in wiki/DependencyMap.md §4.
 //
+// shared/ and engine/ live in the linked @citation-evidence/engine package;
+// boundary rules for those partitions are enforced in citation-engine.
+//
 // Element types (folders) and allowed importers:
-//   shared : importable by every other element (no internal imports of its own).
-//   engine : imports shared.
+//   shared : importable by every other element (package: citation-engine).
+//   engine : imports shared (package: citation-engine).
 //   anchor : imports shared, engine.
 //   source : imports shared, engine.
 //   binder : imports shared, engine, anchor.
 //   work   : imports shared, engine, anchor, source.  (NOT binder.)
 //   app    : imports anything.
-//
-// Path aliases (@shared/*, @engine/*, etc.) come from tsconfig.json paths and
-// are resolved by eslint-import-resolver-typescript.
 
 import js from "@eslint/js";
 import tseslint from "typescript-eslint";
 import boundaries from "eslint-plugin-boundaries";
 import importPlugin from "eslint-plugin-import";
 import globals from "globals";
+import { fileURLToPath } from "node:url";
+import { dirname, resolve } from "node:path";
+
+const __dirname = dirname(fileURLToPath(import.meta.url));
+const engineSrc = resolve(__dirname, "../citation-engine/src");
 
 export default tseslint.config(
   {
@@ -41,8 +46,8 @@ export default tseslint.config(
         typescript: { project: "./tsconfig.json" },
       },
       "boundaries/elements": [
-        { type: "shared", pattern: "src/shared/**" },
-        { type: "engine", pattern: "src/engine/**" },
+        { type: "shared", pattern: `${engineSrc}/shared/**` },
+        { type: "engine", pattern: `${engineSrc}/engine/**` },
         { type: "anchor", pattern: "src/anchor/**" },
         { type: "source", pattern: "src/source/**" },
         { type: "binder", pattern: "src/binder/**" },
@@ -68,4 +73,4 @@ export default tseslint.config(
       ],
     },
   },
-);
+);