feat(FN-2263): merge fusion/fn-2263 (auto-resolved)

- docs(FN-2263): update README with scaffolded scope and deferral documentation
- test(FN-2263): verify hermes runtime plugin build and tests
- feat(FN-2263): implement plugin entrypoint with runtime registration shell
- feat(FN-2263): scaffold Hermes runtime plugin package
- test(FN-2256): add mocks for createResolvedAgentSession in tests
- docs(FN-2256): update architecture docs and add changeset
- fix(FN-2256): fix lint errors and TypeScript issues
- feat(FN-2256): add runtime selection regression tests — Step 4
- feat(FN-2256): route engine session creation through runtime resolver — Step 3
- feat(FN-2256): extend PluginRunner runtime lookup surface — Step 2
- feat(FN-2256): add runtime abstraction and resolver — Step 1

plugins/fusion-plugin-hermes-runtime/vitest.config.ts

@@ -0,0 +1,14 @@
+import { defineConfig } from "vitest/config";
+
+const requestedMaxWorkers = Number.parseInt(process.env.VITEST_MAX_WORKERS ?? "2", 10);
+const maxWorkers = Math.max(1, Math.min(2, Number.isFinite(requestedMaxWorkers) ? requestedMaxWorkers : 2));
+process.env.VITEST_MAX_WORKERS = String(maxWorkers);
+
+export default defineConfig({
+  test: {
+    include: ["src/**/*.test.ts"],
+    pool: "threads",
+    maxWorkers,
+    poolOptions: { threads: { minThreads: 1, maxThreads: maxWorkers }, forks: { minForks: 1, maxForks: maxWorkers } },
+  },
+});