fix(web): correct the dashboard's stylesheet delivery

[Menci]

Stacked on #277.

Summary

Two defects in how the dashboard's CSS reaches the browser.

Utility stylesheet generation. UnoCSS ran in per-module mode, which generates one sheet per module and leaves the bundler to concatenate them in module-graph order. That forfeits UnoCSS's rule ordering, which is a property of a single generate() call. Breakpoint variants landed ahead of the base utilities they override, and since a media query adds no specificity the base utility won at every width — 42 responsive rules across 25 files were inert, among them the sidebar collapse and the mobile navigation trigger.

per-module was itself a workaround: the Vite integration's default global mode emits nothing under React Router. It keys its vite:css-post handle by the top-level build.outDir, while React Router sets outDir only per environment (dist/client, dist/server) and opts into builder.sharedConfigBuild, which is what would otherwise re-resolve the config per environment. The lookup misses and the layer placeholder ships as the entire stylesheet — unocss/unocss#4990, open, and not specific to Vite 8 or Rolldown.

Generating through @unocss/postcss sidesteps that machinery entirely: one pass over the content set is one generate() call, so base utilities, lt-*, and ascending min-width breakpoints emit in that order. The plugin's cwd is pinned to the package, because it resolves both config discovery and the content.filesystem globs against the build process's working directory — without the pin, a build launched from the workspace root emits an empty sheet. The source-level transformers go with the Vite plugin, which was the only thing applying them; neither was reachable, since the source has no variant groups and no CSS files for the directive transformer.

Monospace face. Bundle Cascadia Code through Fontsource and publish it as the theme's fontFamilyMonospace, so code surfaces stop resolving to Courier on macOS. Route UnoCSS's font-mono and every remaining hardcoded monospace declaration through that one token, and override the Prism themes' own font declaration, which addresses the code block through pre[class*="language-"] and outranks a single-class rule. Drop the fontFamilyBase / fontFamilyNumeric overrides, which pinned the bare sans-serif (Helvetica on macOS) in place of Fluent's Segoe UI stack.

Verification

• pnpm run lint
• pnpm run typecheck
• pnpm run test — 420 files, 4,772 tests passed
• pnpm --filter @floway-dev/web run build
• parsed the emitted stylesheet and cross-checked every responsive class against the source: 42 overridden before, 0 after
• confirmed the computed layout at 500, 700, 900, and 1400px in a headless browser, and measured the rendered font-family and loaded @font-face against the running dashboard

[Menci]

Codex agent: Consolidating this follow-up into #277 as requested; the branch remains available while its changes are merged and verified there.