gen-cache-attic 0.1.22

gen — typed cache client (CacheClient trait + AtticClient HEAD-probe impl + NoCacheClient default). Engines consult the trait before triggering builds; substituter hits short-circuit the rebuild. The trait is the swap-in seam for any future binary cache (cachix, S3, R2). Today attic is offline → NoCacheClient is the default; AtticClient activates when the substituter is reachable.

gen-cache-attic — typed cache-probe layer for the gen engine.

The engine consults a [CacheClient] for every derivation before triggering a build. A hit short-circuits the rebuild; a miss flows into the local builder. The trait is the swap-in seam: today's prime impl is [NoCacheClient] (always reports miss); the production impl is [AtticClient] (HEAD-probes the substituter URL). Future impls (cachix, R2, S3) drop in without touching the engine.