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/README.md

@@ -0,0 +1,116 @@
+# Hermes Runtime Plugin
+
+> **Status:** Scaffolded - Full implementation deferred to FN-2264
+
+Provides a Hermes AI runtime plugin for Fusion, enabling AI agent execution capabilities for task automation.
+
+## Overview
+
+This plugin registers the Hermes runtime with the Fusion plugin system. The Hermes runtime is designed to provide AI-powered task execution capabilities for Fusion tasks.
+
+**Note:** The runtime behavior is intentionally deferred. Any runtime invocation will return a "not implemented" signal referencing FN-2264 for the full implementation.
+
+## Features
+
+- **Hermes Runtime Registration**: Registers the Hermes runtime with the Fusion plugin system
+- **Runtime Discovery**: Exposes runtime metadata for plugin discovery pipeline
+- **Runtime Factory**: Provides factory function for runtime instance creation (placeholder)
+
+## Installation
+
+### Option 1: Copy to plugins directory
+
+```bash
+cp -r fusion-plugin-hermes-runtime ~/.fusion/plugins/
+```
+
+### Option 2: Install via CLI
+
+```bash
+fn plugin install /path/to/fusion-plugin-hermes-runtime
+```
+
+## Current Status
+
+| Component | Status |
+|-----------|--------|
+| Plugin Scaffold | ✅ Complete |
+| Runtime Registration | ✅ Complete |
+| Runtime Behavior | ⏳ Deferred to FN-2264 |
+
+## Runtime Registration
+
+The plugin registers a runtime with the following metadata:
+
+- **Runtime ID:** `hermes-runtime`
+- **Name:** `Hermes AI Runtime`
+- **Description:** AI agent execution runtime for Fusion tasks
+- **Version:** `0.1.0`
+
+### Deferred Implementation
+
+The runtime factory currently returns a placeholder object. When `execute()` is called, it throws an error referencing FN-2264:
+
+```
+Error: Hermes runtime is not yet implemented. Full implementation deferred to FN-2264.
+```
+
+## Development
+
+```bash
+# Install dependencies
+pnpm install
+
+# Run tests
+pnpm test
+
+# Build
+pnpm build
+```
+
+### Test Coverage
+
+The plugin includes comprehensive tests covering:
+
+- Plugin manifest identity verification
+- Runtime registration presence and metadata consistency
+- Deferred implementation behavior (placeholder, error on execute)
+- Plugin lifecycle hooks (onLoad, onUnload)
+
+## API
+
+### Plugin Manifest
+
+```json
+{
+  "id": "fusion-plugin-hermes-runtime",
+  "name": "Hermes Runtime Plugin",
+  "version": "0.1.0",
+  "description": "Hermes AI runtime plugin for Fusion",
+  "author": "Fusion Team",
+  "homepage": "https://github.com/gsxdsm/fusion",
+  "runtime": {
+    "runtimeId": "hermes-runtime",
+    "name": "Hermes AI Runtime",
+    "description": "AI agent execution runtime for Fusion tasks",
+    "version": "0.1.0"
+  }
+}
+```
+
+### Exports
+
+The plugin exports the following for testing and verification:
+
+- `default` - The FusionPlugin instance
+- `hermesRuntimeMetadata` - Runtime manifest metadata object
+- `hermesRuntimeFactory` - Factory function for creating runtime instances
+- `HERMES_RUNTIME_ID` - Runtime ID constant (`"hermes-runtime"`)
+
+## Related
+
+- [FN-2264](https://github.com/gsxdsm/fusion/issues/FN-2264) - Full Hermes runtime implementation
+
+## License
+
+MIT