test: assert interaction sequence ordering in consecutive message tests

[BlueHotDog]

Context

The consecutive message tests verify interaction counts (e.g., length(agent_responses) == 2) but don't assert that interactions are in correct sequence order. A broken sequence generator could produce valid counts but corrupt LLM conversation history.

Missing Invariant

Interactions must be monotonically ordered by sequence. Specifically:

• UserMessage1.sequence < AgentResponse1.sequence < AgentCompleted1.sequence < UserMessage2.sequence < AgentResponse2.sequence < AgentCompleted2.sequence
• For tool call flows: ToolCall.sequence < ToolResult.sequence

Proposed Enhancement

In the existing consecutive message tests, add assertions that:

1. All interaction sequences are strictly increasing
2. Each message type appears in the expected position relative to others

File

apps/frontman_server/test/frontman_server/tasks/execution_test.exs