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/src/index.ts

@@ -0,0 +1,96 @@
+/**
+ * Hermes Runtime Plugin
+ *
+ * Provides Hermes AI runtime capabilities for Fusion tasks.
+ * This plugin registers the Hermes runtime with the Fusion plugin system.
+ *
+ * Note: Full runtime behavior is deferred to FN-2264.
+ * Any runtime invocation will return a "not implemented" signal.
+ */
+
+import { definePlugin } from "@fusion/plugin-sdk";
+import type {
+  FusionPlugin,
+  PluginContext,
+  PluginRuntimeFactory,
+  PluginRuntimeManifestMetadata,
+} from "@fusion/plugin-sdk";
+
+// ── Hermes Runtime Metadata ───────────────────────────────────────────────────
+
+const HERMES_RUNTIME_ID = "hermes-runtime";
+const HERMES_RUNTIME_VERSION = "0.1.0";
+
+const hermesRuntimeMetadata: PluginRuntimeManifestMetadata = {
+  runtimeId: HERMES_RUNTIME_ID,
+  name: "Hermes AI Runtime",
+  description: "AI agent execution runtime for Fusion tasks",
+  version: HERMES_RUNTIME_VERSION,
+};
+
+// ── Hermes Runtime Factory ────────────────────────────────────────────────────
+
+/**
+ * Factory function for creating the Hermes runtime instance.
+ *
+ * This is a placeholder implementation. Full runtime behavior is deferred to FN-2264.
+ * Any runtime invocation will throw a descriptive error referencing FN-2264.
+ *
+ * @param _ctx - Plugin context (unused in placeholder)
+ * @throws Error with message referencing FN-2264 for full implementation
+ */
+const hermesRuntimeFactory: PluginRuntimeFactory = (_ctx: PluginContext) => {
+  // Return a placeholder object that signals deferred implementation
+  return {
+    runtimeId: HERMES_RUNTIME_ID,
+    version: HERMES_RUNTIME_VERSION,
+    status: "deferred",
+    message: `Hermes runtime implementation is deferred to FN-2264. ` +
+             `Current invocation is a placeholder.`,
+    execute: async () => {
+      throw new Error(
+        `Hermes runtime is not yet implemented. ` +
+        `Full implementation deferred to FN-2264. ` +
+        `See https://github.com/gsxdsm/fusion/issues/FN-2264`,
+      );
+    },
+  };
+};
+
+// ── Plugin Definition ─────────────────────────────────────────────────────────
+
+const plugin: FusionPlugin = definePlugin({
+  manifest: {
+    id: "fusion-plugin-hermes-runtime",
+    name: "Hermes Runtime Plugin",
+    version: "0.1.0",
+    description: "Hermes AI runtime plugin for Fusion - provides AI agent execution runtime capabilities",
+    author: "Fusion Team",
+    homepage: "https://github.com/gsxdsm/fusion",
+    runtime: hermesRuntimeMetadata,
+  },
+  state: "installed",
+  hooks: {
+    onLoad: (ctx) => {
+      ctx.logger.info("Hermes Runtime Plugin loaded (placeholder - FN-2264 pending)");
+      ctx.emitEvent("hermes-runtime:loaded", {
+        runtimeId: HERMES_RUNTIME_ID,
+        version: HERMES_RUNTIME_VERSION,
+        status: "deferred",
+      });
+    },
+    onUnload: () => {
+      // No context available during unload
+    },
+  },
+  runtime: {
+    metadata: hermesRuntimeMetadata,
+    factory: hermesRuntimeFactory,
+  },
+});
+
+export default plugin;
+
+// ── Exports for Testing ───────────────────────────────────────────────────────
+
+export { hermesRuntimeMetadata, hermesRuntimeFactory, HERMES_RUNTIME_ID };