feat: type the plugin host record, move plugin strings out of core and add lint checks

scripts/check-test-locations.test.ts

@@ -0,0 +1,57 @@
+import { afterEach, describe, expect, it } from "vitest";
+import { createRequire } from "node:module";
+import fs from "node:fs";
+import os from "node:os";
+import path from "node:path";
+
+const require = createRequire(import.meta.url);
+const { misplaced } = require("./check-test-locations.cjs") as {
+  misplaced: (root: string) => string[];
+};
+
+let root: string | null = null;
+
+afterEach(() => {
+  if (root) fs.rmSync(root, { recursive: true, force: true });
+  root = null;
+});
+
+function fixture(files: string[]): string {
+  root = fs.mkdtempSync(path.join(os.tmpdir(), "test-locations-"));
+  for (const file of files) {
+    const full = path.join(root, file);
+    fs.mkdirSync(path.dirname(full), { recursive: true });
+    fs.writeFileSync(full, "");
+  }
+  return root;
+}
+
+describe("misplaced", () => {
+  it("accepts the mirrored test trees", () => {
+    const dir = fixture([
+      "src/backend/tests/utils/a.test.ts",
+      "src/ui/tests/lib/b.test.tsx",
+      "scripts/c.test.ts",
+      "plugins/docker/tests/backend/d.test.ts",
+      "plugins/docker/node_modules/pkg/e.test.ts",
+      "plugins/docker/dist/f.test.ts",
+    ]);
+    expect(misplaced(dir)).toEqual([]);
+  });
+
+  it("refuses a test next to its source", () => {
+    const dir = fixture([
+      "src/backend/utils/a.test.ts",
+      "src/ui/lib/b.test.tsx",
+      "plugins/docker/src/frontend/c.test.tsx",
+      "packages/plugin-sdk/src/d.test.ts",
+      "src/backend/utils/not-a-test.ts",
+    ]);
+    expect(misplaced(dir)).toEqual([
+      "packages/plugin-sdk/src/d.test.ts",
+      "plugins/docker/src/frontend/c.test.tsx",
+      "src/backend/utils/a.test.ts",
+      "src/ui/lib/b.test.tsx",
+    ]);
+  });
+});