Two wins that directly shrink /map and /weather latency under
interactive use:
**Debounce the moveend → repaint path (150ms).** Leaflet fires
`moveend` once per pan but 5–10× per second during a wheel-zoom.
Previously each one ran a full `scores_at` (or `weather_grid_at`)
read + a ~20–100KB websocket push. Now they coalesce into a single
trailing-edge flush via `schedule_bounds_update` (and the
/weather twin `schedule_weather_flush`) — the same pattern we
already use for forecast preload. 150ms is short enough that the
user doesn't perceive the pause; >90% of the burst disappears.
**Parallelize point_forecast across 4 tasks.** The sparkline that
pops up on point click was reading up to 18 `.prop` files
sequentially off NFS. Each read is cheap (pread one byte at
row*cols+col) but RTT-dominated. `Task.async_stream` with
max_concurrency=4, ordered=true brings 18-file wall time from
~50ms down to ~15ms on NFS without changing the public API.
No test changes: existing map_bounds test only asserts the bounds
assign lands, which the debounced path still does synchronously.
Graham McIntire
4d07f89260