Architecture decisions

Each record describes one decision already taken in this codebase, the context, and the consequences. Add a new record with the next number when you change one of them.

ADR	Decision
0001	Money is Decimal end to end
0002	A deterministic offline extractor is the default; the LLM extractor is optional
0003	The decision is the strictest severity among the reasons
0004	One tag-driven release path