Two coupled changes addressing the 2026-05-26 validate-neuron failure
where a fresh deploy of beast had /health unreachable for ~5 minutes
while Qwen3.6-27B q5k materialised, even though systemd reported the
unit as active.
1. main.rs no longer awaits load_default_models before binding axum.
The listener binds first; pre-warm runs in a spawned background
task that holds a read lock on the harness registry for the
duration of its sequential load loop. Concurrent on-demand
/models/load and /v1/chat/completions traffic still flow.
2. /health gains an `activation` field carrying:
state pre_warming | ready
pending model ids queued but not started
in_progress model id currently loading (Option)
completed model ids loaded successfully this activation
failed [{model_id, error}] for failed entries
The field is `#[serde(default)]` so a pre-change cortex polling a
new neuron — or vice versa — keeps working.
`ActivationTracker` (new module `neuron::activation`) owns the
RwLock-wrapped state; load_default_models takes a tracker reference
and updates it per-model. NeuronState holds an Arc clone for the
/health handler.
Tests updated to construct trackers and assert state transitions
(empty noop, two failures → ready with both in `failed`).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
