Fills the three gaps left by the orchestrator/width-depth salvage:
- configuration.md §Delegation: max_concurrent_children, max_spawn_depth,
orchestrator_enabled are now in the canonical config.yaml reference
with a paragraph covering defaults, clamping, role-degradation, and
the 3x3x3=27-leaf cost scaling.
- environment-variables.md: adds DELEGATION_MAX_CONCURRENT_CHILDREN to
the Agent Behavior table.
- features/delegation.md: corrects stale 'default 5, cap 8' wording
(that was from the original PR; the salvage landed on default 3 with
no ceiling and a tool error on excess instead of truncation).
bf73ced4f5