feat: introduce workflow management tools and commands

- Added new workflow commands: `/workflow` to open the workflow panel and `/workflow run <prompt>` to execute workflows.
- Implemented `spawn_agents` and `spawn_pipeline` tools for parallel and sequential task execution, respectively.
- Enhanced workflow engine to handle real-time agent status updates and display in the UI.
- Updated workflow panel to show agent statuses, findings count, and session counters.
- Refactored existing code to integrate new workflow functionalities and improve overall structure.

src/app/runtime/commands.rs

@@ -81,6 +81,12 @@ pub fn apply_command(command: Command) -> Vec<Action> {
         Command::Compact => {
             vec![Action::Compact]
         }
+        Command::WorkflowOpen => {
+            vec![Action::OpenOverlay(Overlay::Workflow)]
+        }
+        Command::WorkflowRun { script } => {
+            vec![Action::RunWorkflow { script }]
+        }
         Command::Unknown(cmd) => {
             vec![Action::SystemNote {
                 kind: "error".to_string(),