Decision Record (ADR)

Write a short file docs/decisions/NNN-<slug>.md:

• Context — what forced a decision. The constraints.
• Options — the 2-3 real candidates, one line each.
• Decision — what you picked, dated.
• Why — the tradeoff. What you gave up. "We picked Postgres over Mongo because we need real joins; we accept heavier ops."
• Consequences — what this now makes easy and hard. Hard-to-reverse choices (schema, auth, data store) MUST get one. Future-you will ask "why on earth did we do this" — answer it now.