[BUG] Prevent inconsistent CommandResponse status and failure telemetry

### Describe the bug

`CommandResponse` can represent contradictory state because its status, results, and `TelemetryFailureMessage` are independently mutable. The telemetry pipeline currently records `TelemetryFailureMessage` only when `response.Status` is outside the 2xx range.

If command code catches an exception or encounters another failure, populates `TelemetryFailureMessage`, but accidentally leaves the default success status, the response becomes a "task failed successfully": the failure is reported as success and the diagnostic telemetry message is silently ignored.

This was identified in the review of #3426: https://github.com/microsoft/mcp/pull/3426#discussion_r3910815532

### Expected behavior

Contradictory `CommandResponse` state should be prevented or detected. A command should not be able to return a successful status together with failure-only telemetry without a clear signal.

Consider introducing construction APIs that encode valid outcomes, such as `CommandResponse.FromSuccess(...)`, `CommandResponse.FromException(...)`, and `CommandResponse.FromNonExceptionFailure(...)`, and/or validation that rejects inconsistent combinations. If compatibility prevents enforcing invariants immediately, emitting `TelemetryFailureMessage` regardless of status could provide interim detection for incorrectly classified failures.

### Actual behavior

`CommandResponse` defaults to HTTP 200 and exposes mutable properties. A command can set `TelemetryFailureMessage` while leaving `Status` successful. The response is treated as successful and the telemetry failure message is not emitted.

### Reproduction Steps

1. Implement a command that returns its default `CommandResponse`.
2. Simulate a failure path that sets `context.Response.TelemetryFailureMessage` but does not update `context.Response.Status`.
3. Return the response.
4. Observe that the command result has a successful status and `ToolFailureMessage` is absent from telemetry.

### Environment

Shared `Microsoft.Mcp.Core` command response and telemetry pipeline. Observed while reviewing PR #3426.