Session search and self-configuration move to CLI commands

Yolop 0.18.0 removes several model tools and routes the same work through CLI commands that the agent runs in its shell:

• search_sessions is replaced by yolop sessions search and yolop sessions list. The session_history capability ID is now sessions.
• list_mcp_servers, set_reasoning_effort, search_models, set_model, set_provider and the connector tools are removed. Use yolop mcp, the provider and model commands, and the new yolop connectors list|get|connect|disconnect.
• Capability IDs drop the yolop_ prefix: yolop_approval is now approval.

Upgrade note: settings overrides that use the old capability IDs fail validation. Rename them to the bare IDs.

See CLI essentials, #691 and #693.