Refactor agent execution to use AgentRun with OpenAI-compatible API

Major refactoring to support isolated run objects with streaming, events, and OpenAI-compatible endpoints.

## Backend Changes

- **Agent class**: Added `run()` method, `received_message()` wraps chat into AgentRun
- **AgentRun class**: New class for run state with event system, serialization, and user tracking
- **inference.py**: Complete refactor with `build_messages()`, `chat_completion()`, tool support for llama-cpp/ollama/replicate
- **tools.py**: New centralized tool management (ToolSpec, ToolParameter, format_tools_for_engine)
- **tools.py**: Removed legacy Toolset/Action/ToolDescription system
- **server.py**: Added OpenAI-compatible `/api/openai/v1/chat/completions` endpoint with streaming support
- **temporary.py**: Added `self.runs` dict to State class
- **expert.py**: Refactored to use new Agent.run() signature
- **scripted.py**: Updated to raise NotImplementedError

## Frontend Changes

- **backend.js**: Added `onRunEvents()` for run event subscriptions
- **Sidebar.vue**: Added runs navigation mode
- **router/index.js**: Renamed User route to RunsView
- **RunsView.vue**: New view for listing/monitoring agent runs

## Breaking Changes

- Agent `prompt()` signature changed: `(instruction, input=None, **kwargs)` instead of `(content)`
- Agent `received_message()` must use AgentRun pattern
- Tools.py removed, functionality moved to tool.py
- Deprecated tool prompt/action system removed

frontend/src/components/main/Sidebar.vue

@@ -101,6 +101,8 @@
         </button>
       </div>
     </div>
+    <nav v-if="mode=='runs'">
+    </nav>
     <nav v-if="mode=='chats'">
       <RouterLink v-for="it in chats" :to="'/chat/' + it.id" class="nav-item">{{it.name}}</RouterLink>
       <RouterLink to="/chat/create" class="nav-item">Create Chat</RouterLink>
@@ -110,8 +112,9 @@
       <RouterLink to="/agent/create" class="nav-item">Create Agent</RouterLink>
     </nav>
     <nav v-if="mode=='settings'">
-      <RouterLink to="/models" class="nav-item">Manage Models</RouterLink>
       <RouterLink to="/user" class="nav-item">User</RouterLink>
+      <RouterLink to="/models" class="nav-item">Manage Models</RouterLink>
+      <RouterLink to="/runs" class="nav-item">Agent Runs</RouterLink>
     </nav>
   </aside>
 </template>