docs: aviation flavor — airspace regions, ops manual, Airworthiness Directives

[jonatw-eagle]

Finishes the aviation-metaphor layer, terms verified against SKYbrary/EASA:

• README — each lane is a region of airspace with its own flight rules (scope/conventions/what it may touch); an agent's skills are its operations manual.
• agentic-iac — a security update or must-do change is an Airworthiness Directive: mandatory, deadline-bound, and an overdue AD blocks the release-to-service (you can't sign it off / merge with a critical fix outstanding) — the mandatory counterpart to the deferrable MEL.

Flavor, not the mechanism; technical content unchanged.