Drop Tailwind for plain CSS modules

[kcarnold]

Rebased onto main now that #621 and #623 have landed.

The app only ever used a thin layer of Tailwind utilities, mostly for layout and one-off colors. This ports the remaining ones to CSS modules alongside the styles they sit next to, and removes the toolchain.

Preflight is the load-bearing part

@import 'tailwindcss' brings in Tailwind's reset, and this app leans on it hard: nearly every CSS module assumes zeroed margin/padding/border and universal box-sizing: border-box, but only a handful declare box-sizing themselves. It also supplies font: inherit on form controls and a { color: inherit; text-decoration: inherit }. So preflight is vendored as src/preflight.css — verbatim, with --theme(--x, fallback) calls resolved to their fallbacks.

It stays in @layer base, where @import 'tailwindcss' put it. The layer matters as much as the contents: unlayered CSS beats layered CSS regardless of specificity, which is exactly what lets components/markdown/styles.module.css (from #621) put list markers and heading sizes back with a single class and no !important. Vendoring preflight unlayered would silently flip those contests. Verified @layer base survives into the emitted CSS.

Doc and comment updates

Four places attributed the reset to Tailwind. The mechanism they describe is unchanged — only the source moves, and @layer base still holds:

• docs/markdown-rendering.md (intro + the preflight section)
• frontend/CLAUDE.md
• components/markdown/index.tsx
• components/markdown/styles.module.css

editor/styles.css no longer exists, so references to it are gone too.

Build and dependency effects

• 41 packages leave the lockfile, including the native @tailwindcss/oxide and lightningcss binaries for all 9 target platforms — the meaningful win for Docker build time and image size.
• postcss.config.js collapses to reshaped's config, unwrapped.
• eslint no longer references a tailwind.config.js that never existed here.

Also dropped as dead

• @tailwindcss/typography and the .prose rules in taskpane.css — nothing ever applied a prose class, and Fix markdown rendering in Chat: tables, list formatting, and doctext citations #621 wrote its own .markdown element styles rather than using it.
• The .container input block in logs/styles.module.css — container is a DOM id (getElementById('container')), so that CSS-module class never matched anything. Fix markdown rendering in Chat: tables, list formatting, and doctext citations #621 noted the file was imported nowhere; this branch imports it and drops the dead block.
• editor/styles.css, which had nothing left but the two Tailwind imports.

Colors

Ported values are the v4 palette. Tailwind v4 ships colors in oklch, so v3 hex codes are wrong here — blue-300 is #8ec5ff, not #bfdbfe (that's blue-200), and blue-500, green-500 and red-600 all differ visibly. Values were converted from theme.css rather than transcribed, so this should be a pixel no-op and needs no snapshot regeneration.

Verified

npm run typecheck, npm run lint, npm test (239 passing), npm run format:check (unchanged at 5 pre-existing warnings), npm run build, and BUILD_TARGET=google-docs vite build.

🤖 Generated with Claude Code