CLI does not support all IInteractionService prompt types during pipeline execution

## Problem

`IInteractionService` exposes several prompt methods, but the CLI only supports a subset during pipeline execution:

| Method | Supported in CLI | What happens |
|--------|-----------------|-------------|
| `PromptInputsAsync` | ✅ Yes | Renders as input form |
| `PromptNotificationAsync` | ✅ Yes | Renders as boolean confirm |
| `PromptConfirmationAsync` | ❌ No | **Hangs forever** |
| `PromptMessageBoxAsync` | ❌ No | **Hangs forever** |

When a pipeline step calls an unsupported method, the interaction is silently dropped by `PipelineActivityReporter.WriteInteractionUpdateToClientAsync` and the call blocks indefinitely waiting for a response that never arrives. No error, no timeout, no log — just a hang.

## Impact

Pipeline step authors who use `PromptConfirmationAsync` (the natural API for yes/no questions) get a silent hang. The workaround is to use `PromptNotificationAsync` instead, which is not discoverable.

## Suggested fix

Either:
1. Add CLI support for all `IInteractionService` prompt types
2. Or throw / log a warning when an unsupported interaction type is used during pipeline execution, instead of silently dropping it