perf(web): reduce dashboard rendering cost and spectrum payloads#133

fix(web): isolate clip paths for each chart instance

perf(web): load file details once per navigation

perf(web): request only the displayed spectrum side

perf(web): use Zod Mini for client validation

perf(web): batch coverage geometry while retaining bucket observations

perf(web): reuse temporal labels and layout formatting

perf(web): rasterize dense spectrum marks without sampling

perf(web): paint focus rings only for focused observations

perf(web): mount charts directly through the DOM host