The second lived-spine half: the engine learns WHILE IT LIVES, not only when
prompted. ChatRuntime.idle_tick() advances the contemplation/proposal flywheel
between turns (no user input):
- contemplates the pending discovery backlog (enrichment), then runs the
replay-gated propose_from_candidate into a persistent, file-backed ProposalLog
(engine_state/proposals.jsonl) held on the runtime.
- PROPOSAL-ONLY: it never ratifies. Raw cold-start candidates are 'undetermined'
and the eligibility gate refuses them outright (the engine won't propose what
it hasn't determined). A determined candidate only reaches 'pending' — moving
to 'accepted'/corpus-append stays HITL via teaching/review. No idle tick emits
an accepted / accepted_corpus_append event.
- The proposal log and the candidate backlog both live in the engine-state dir,
so idle learning persists across reboot and accumulates (CL-2) — building on
Shape B+ resume + L11 identity continuity.
idle_tick returns IdleTickResult(candidates_contemplated, proposals_created,
pending_proposals). None proposal log under no_load_state (ephemeral runtimes
keep no learning lineage).
5 dedicated tests: no-op on empty backlog, contemplates the backlog, refuses
undetermined (safety), proposes-a-determined-candidate-but-never-ratifies,
idle-learning-persists-across-reboot.
