Lambda prompt (λ) appears in interactive sessions with workspace chat.defaultAgent

Description:
When running kiro-cli chat --trust-all-tools in an interactive terminal session, the prompt incorrectly shows the lambda symbol [MyAgent] λ !> instead of
the standard interactive prompt [MyAgent] !>.

The lambda symbol should only appear when the agent is invoked programmatically (e.g., via shell scripts), not during normal interactive chat sessions.

Steps to Reproduce:
1. Navigate to a workspace directory (e.g., ~/my-project/)
2. Create workspace-specific Kiro settings: .kiro/settings/cli.json
3. Add the following content:
json
{
"chat.defaultAgent": "MyAgent"
}

4. Run kiro-cli chat --trust-all-tools from that directory
5. Observe the prompt shows [MyAgent] λ !> with the lambda symbol

Expected Behavior:
The prompt should display [MyAgent] !> (without lambda symbol) for interactive terminal sessions, regardless of workspace settings.

Actual Behavior:
The prompt displays [MyAgent] λ !> (with lambda symbol), incorrectly indicating programmatic/non-interactive mode.

Environment:
- Kiro CLI version: 1.25.1
- OS: macOS
- Agent: Custom agent
- Setting location: Workspace-specific .kiro/settings/cli.json