A dedicated learning-path conversation agent

The learning-path conversation now has a dedicated native agent with typed scoped messages, clarifying questions, generation requests and unrelated-request redirects. It receives only the learner's confirmed, relevant context for each turn and can search existing roles and skills through read-only tools. Catalogue selections and retained learner facts are validated before the backend can accept them. The agent continues through the shared private message history and records model and tool usage through the existing observability service. Routes and path generation remain inactive until their later integration checkpoints.