feat(web): community site for deepseek-tui.com (mobile + color refresh) (#1108)

First commit of the Next.js community site that powers
deepseek-tui.com, deployed via Cloudflare Workers / OpenNext.

This commit lands the scaffold and applies the visual + correctness
pass requested by community feedback:

- Palette: drop the cream/Anthropic-feel paper (#F4F1E8) for a
  DeepSeek-aligned cool white + soft gray (#FFFFFF / #F4F6FB), with
  indigo accents kept. Soften default hairlines so a pure-white
  background reads clean instead of harsh.
- Mobile: add a hamburger menu (mobile-menu.tsx) so phones can reach
  Install / Docs / Activity / Roadmap / Contribute — previously the
  link list was hidden on phones with no replacement. Tighter hero,
  flexible button row, viewport-safe code blocks, columnar grids
  collapse cleanly under 768px, and the printed-almanac center rule
  is desktop-only now (it sliced through narrow viewports).
- "How it works" diagram: replace the hand-rolled ASCII art (which
  misaligned under CJK monospace because Han characters take 2
  columns vs Latin's 1, per dhh's note in WeChat) with a real
  mermaid diagram rendered client-side via dynamic import. Uses the
  mermaid.live standard syntax 庄表伟 recommended.
- Issue #1104: the docs listed a `deepseek-cn` provider that the
  v0.8.16 binary doesn't accept (`ProviderArg` in crates/cli only
  has 9 variants; the 10th lives only in the legacy tui/config.rs).
  derive-facts.mjs now omits `deepseek-cn` until that variant is
  wired through the shared ProviderKind, and the install page's
  China-network recipe uses `base_url` / `DEEPSEEK_BASE_URL` (which
  actually works on v0.8.16) instead of the unsupported provider.

Auto-deploys via .github/workflows/deploy-web.yml on push to main.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.github/workflows/deploy-web.yml

@@ -0,0 +1,76 @@
+name: deploy-web
+
+# Auto-deploys deepseek-tui.com (Cloudflare Worker) on every push to main that
+# touches the web app or any source the site auto-derives facts from.
+#
+# Required repo secret:
+#   CLOUDFLARE_API_TOKEN — token with Workers Scripts:Edit + Workers KV:Edit
+#                          + Workers Custom Domain:Edit on this account.
+#
+# Manual trigger via the Actions tab is also supported.
+
+on:
+  push:
+    branches: [main]
+    paths:
+      - "web/**"
+      - "Cargo.toml"
+      - "crates/tui/src/config.rs"
+      - "crates/tui/src/sandbox/**"
+      - "crates/tui/src/main.rs"
+      - "npm/deepseek-tui/package.json"
+      - "CHANGELOG.md"
+      - ".github/workflows/deploy-web.yml"
+  workflow_dispatch:
+
+concurrency:
+  group: deploy-web
+  cancel-in-progress: false
+
+jobs:
+  deploy:
+    runs-on: ubuntu-latest
+    timeout-minutes: 15
+    permissions:
+      contents: read
+    defaults:
+      run:
+        working-directory: web
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 20
+          cache: npm
+          cache-dependency-path: web/package-lock.json
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Lint
+        run: npm run lint
+
+      - name: Build (Next.js)
+        run: npm run build
+
+      - name: Build (OpenNext for Cloudflare)
+        run: npx opennextjs-cloudflare build
+
+      - name: Verify KV ids configured
+        run: npm run predeploy
+
+      - name: Deploy to Cloudflare
+        env:
+          CLOUDFLARE_API_TOKEN: ${{ secrets.CLOUDFLARE_API_TOKEN }}
+        run: npx wrangler deploy
+
+      - name: Refresh fact drift after deploy
+        if: success()
+        env:
+          CRON_SECRET: ${{ secrets.CRON_SECRET }}
+        run: |
+          if [ -n "$CRON_SECRET" ]; then
+            curl -fsS -H "x-cron-secret: $CRON_SECRET" \
+              "https://deepseek-tui.com/api/cron?task=facts-drift" || true
+          fi