This branch's two RFCs (prompt-variables, provider-lifecycle events)
conform to the new contract in the same merge: 'Status: implemented'
dateless header, 'Rejected alternatives' -> 'Alternatives considered',
'What we give up' folded into '## Consequences' (per the uniform-format
RFC's own rejection of a costs-only closer), and the index regenerated
into the new INDEX.md. docs/rfc/README.md resolved to master's rewrite.