"""Planner agent — slow-path CRISP-DM analysis planner.

Single LLM call: BusinessContext + CatalogSummary + ToolRegistry + question +
Constraints -> a validated, static `TaskList` (a DAG of fully-specified
tool-call chains). No replanning (INV-6); tool-agnostic (INV-7).

See AGENT_ARCHITECTURE_CONTEXT_new.md §7.3.
"""