perf: eliminate Three.js/WebGL, fix render-blocking CSS, add dev team agents

- Replace ShaderGradientBackground WebGL shader (3 static spheres) with pure
  CSS radial-gradient divs — moves from ClientProviders (deferred JS) to
  app/layout.tsx as a server component rendered in initial HTML. Eliminates
  @shadergradient/react, three, @react-three/fiber from the JS bundle.
  Removes chunks/7001 (~20s CPU eval) and the 39s main thread block.

- Remove optimizeCss/critters: it was converting <link rel="stylesheet"> to a
  JS-deferred preload, which PageSpeed read as a 410ms sequential CSS chain.
  Both CSS files now load as parallel <link> tags from initial HTML (~150ms).

- Update browserslist safari >= 15 → 15.4 (Array.prototype.at, Object.hasOwn
  are native in 15.4+; eliminates unnecessary SWC compatibility transforms).

- Delete orphaned app/styles/ghostContent.css (never imported anywhere, 3.7KB).

- Add .claude/ dev team setup: 5 subagents (frontend-dev, backend-dev, tester,
  code-reviewer, debugger), 3 skills (/add-section, /review-changes,
  /check-quality), 3 path-scoped rules, settings.json with auto-lint hook.

- Update CLAUDE.md with server/client orchestrator pattern, SSR animation
  safety rules, API route conventions, and improved command reference.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.claude/skills/add-section/SKILL.md

@@ -0,0 +1,50 @@
+---
+name: add-section
+description: Orchestrate adding a new CMS-managed section to the portfolio following the full 6-step pattern
+context: fork
+agent: general-purpose
+---
+
+Add a new CMS-managed section called "$ARGUMENTS" to the portfolio.
+
+Follow the exact 6-step pattern from CLAUDE.md:
+
+**Step 1 — lib/directus.ts**
+Read `lib/directus.ts` first, then add:
+- TypeScript interface for the new collection
+- `directusRequest()` GraphQL query for the collection (with translation support if needed)
+- Export the fetch function
+
+**Step 2 — API Route**
+Create `app/api/$ARGUMENTS/route.ts`:
+- `export const runtime = 'nodejs'`
+- `export const dynamic = 'force-dynamic'`
+- Try Directus first, fallback to hardcoded defaults
+- Include `source: "directus" | "fallback" | "error"` in response
+- Error logging behind `process.env.NODE_ENV === "development"` guard
+
+**Step 3 — Component**
+Create `app/components/$ARGUMENTS.tsx`:
+- `"use client"` directive
+- Skeleton loading state for the async data
+- Tailwind liquid-* tokens for styling (cards: `bg-gradient-to-br from-liquid-*/15 via-liquid-*/10 to-liquid-*/15 backdrop-blur-sm border-2 rounded-xl`)
+- Headline uppercase with tracking-tighter and emerald accent dot
+
+**Step 4 — i18n**
+Add translation keys to both:
+- `messages/en.json`
+- `messages/de.json`
+
+**Step 5 — Client Wrapper**
+Add `${ARGUMENTS}Client` to `app/components/ClientWrappers.tsx`:
+- Wrap in scoped `NextIntlClientProvider` with only the needed translation namespace
+
+**Step 6 — Homepage Integration**
+Add to `app/_ui/HomePageServer.tsx`:
+- Fetch translations in the existing `Promise.all`
+- Render wrapped in `<ScrollFadeIn>`
+
+After implementation:
+- Run `npm run lint` — must be 0 errors
+- Run `npm run build` — must compile successfully
+- Report what was created and any manual steps remaining (e.g., creating the Directus collection)