* refactor: remove `useChatContext` from `useSelectMention`, explicitly pass `conversation` object
* feat: ephemeral agents via model specs
* refactor: Sync Jotai state with ephemeral agent state, also when Ephemeral Agent has no MCP servers selected
* refactor: move `useUpdateEphemeralAgent` to store and clean up imports
* refactor: reorder imports and invalidate queries for mcpConnectionStatus in event handler
* refactor: replace useApplyModelSpecEffects with useApplyModelSpecAgents and update event handlers to use new agent template logic
* ci: update useMCPSelect test to verify mcpValues sync with empty ephemeralAgent.mcp