Rust `prop-grid-rs` has been validated end-to-end on talos5 on the
streamed-bands image (main-1776635096-6d91461): real chain steps
complete in ~7 s each and the peak-heap refactor landed.
Changes:
- `PropagationGridWorker.seed_chain` now enqueues a single f00 Oban
job instead of f00–f18. The f00 analysis-hour keeps its enrichment
(native-level duct, NEXRAD composite, commercial-link boost,
ProfilesFile write) and the GridCache broadcast.
- `GridTaskEnqueuer.seed/1` is called again so grid_tasks gets the
18 forecast-hour rows the Rust worker claims.
- Test asserts only one Oban job is enqueued and the matching 18
grid_tasks rows land in the DB.
- `deployment-grid-rs.yaml` flips `PROP_SCORES_DIR` from
`/data/scores_shadow` to `/data/scores` so Rust writes to the live
score tree. No file collision — Elixir only writes the f00 files.
The hot pod memory shrink (6 Gi → 1 Gi) is deferred until one full
hourly cycle runs clean under the new split.