* feat(perf): add on-demand (ui) throughput to cover pipeline cpm
Cover cpm previously measured only the native backfill (lib) via the
cover:library-progress done delta. Add a parallel UI series: every completed
on-demand Rust cover ensure (grid / now-playing) records a timestamp, surfaced
as a covers-per-minute rate. Both are exposed in the live cover diag, shown as
separate Backfill (lib) / On-demand (ui) cards in the Monitor tab (each pinnable
to the overlay) and as lib/ui rows in the Cover pipeline overlay block.
* docs(changelog): note cover on-demand (ui) throughput (PR #947)
Add CHANGELOG entry and credits line for the UI cover cpm metric.
* fix(perf): source on-demand (ui) cpm from backend produced-cover count
The JS ensure-queue counter never tracked: produced covers return hit:true
(only misses/errors are hit:false), and ensure-queue dedup/HMR made client
counting unreliable. Count on-demand covers natively in ensure_inner on the
produce path (non-bulk, past the cache-hit gate), expose a cumulative
uiEnsuredTotal in the pipeline stats, and derive the per-minute rate on the
frontend from polled deltas — mirroring the lib backfill series.
* perf(cover): measure cpm over trailing 5s instead of full minute
A 60s rolling average added too much inertia, flattening real bursts and
stalls in both the lib backfill and on-demand (ui) cover throughput. Compute
the rate from the trailing 5s of samples (still extrapolated to per-minute),
so the figure reacts promptly and decays to 0 within the window when idle.
* feat(perf): cover pipeline throughput (cpm) in performance probe
Mirror the analysis pipeline's tpm for covers. A new coverPerfStore samples the
backfill `done` progress from cover:library-progress events and derives a rolling
one-minute covers-per-minute rate. Surfaced as a live diag in perfLiveStore, a
pinnable "Cover backfill" throughput card in the Monitor tab, and a cpm row in
the Cover pipeline overlay block.
* docs(changelog): note cover pipeline cpm metric (PR #945)
Add CHANGELOG entry and credits line for the cover-pipeline covers-per-minute
throughput metric in the Performance Probe.
cucadmuh