Add first-class runtime mode support for long-lived and request-based agent execution

### Language Implementation

- [ ] Python
- [ ] TypeScript

### Feature Type

- [ ] Action Provider Template
- [ ] Wallet Provider Template
- [ ] Framework Extension
- [ ] Core Requirements
- [ ] Other

### 🚀 The feature, motivation and pitch

## Overview
AgentKit agents can run in both long-lived processes (workers, daemons) and request-based environments (serverless, APIs), but the framework does not currently expose explicit runtime modes or helpers optimized for these different execution models.

## Problem Description
Without runtime-specific support:
- Developers must manually adapt lifecycle, retries, and cleanup logic.
- Agents may behave inefficiently in serverless environments.
- Long-lived agents lack clear conventions for persistence and shutdown handling.

## Proposed Solution
Add explicit runtime modes (e.g. `longLived` and `requestScoped`) that adjust default behavior for retries, cleanup, and execution boundaries, while still allowing customization.

### Acceptance Criteria
AgentKit provides clear runtime modes with sensible defaults. Developers can choose the appropriate mode without reinventing lifecycle logic. Existing integrations continue to work without changes.

### Alternatives

_No response_

### Additional context

_No response_