0.5.x

The MVP line (owner definition 2026-09-23): follow-on work ships as 0.5.N patch releases until every issue here is resolved; the release that closes this milestone is the initial MVP and may take the deliberate minor bump to 0.6.0. In scope: the mentor writes to the learning tier (plan item 1 — the one MVP blocker: zero writer calls in 143,973 messages), D-E age-aware nudge + retire/snooze (#26), pi core-tier conditions discharged (#21, re-scoped to its pi boxes). Owner decisions for the learning-tier plan (#34). Moved to 0.6.0 on 2026-09-23: #31, #33, OpenCode-to-core, Jev measurement.