Slice 5: Add drilldowns, detail routes, and persistent filters

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Objective

Make the overview actionable instead of decorative.

Tasks

• Add day detail route
• Add model detail route
• Add tool detail route
• Add table sorting and paging
• Preserve filter state in search params so views are shareable

Acceptance criteria

• Users can move from summary panels to focused detail views
• Filter state survives refresh and shared URLs
• Detail views reconcile to the top-line dashboard numbers

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Responsive pass now needs to be treated as part of the frontend acceptance, not a nice-to-have.

What was addressed on the monorepo branch / PR #14:

• header actions stack cleanly on mobile
• tabs can scroll horizontally instead of clipping
• toolbar chips/search collapse to single-column at smaller widths
• KPI cards move to a 2-column tablet layout
• signals rows stop fighting horizontal space
• daily rollups table hides lower-priority columns at smaller breakpoints and keeps trace ID inline under the date

Net: mobile is materially better, but future dashboard slices should preserve breakpoint behavior as drilldowns and filters are added.

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Related comparison UX follow-up: issue #16 tracks dual-source plotting/filtering behavior so drilldowns and persistent filters can stay source-aware when more than one usage feed exists.

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Picking this up now. I am treating it as a dependent branch off the monorepo PR, with the first pass focused on: shareable search-param filters, sortable/paged daily rollups, and concrete day/model detail routes.