fix: streamline settings and context status

Settings Center navigation was hard to read and constrained form content,
while Runtime customization duplicated headings and save actions and could
lose drafts. Settings now uses readable navigation and wider content, saves
base and native Runtime settings together, protects drafts, and presents one
compact capabilities and defaults section.

Conversation context meters could retain display-only thresholds from old
Runtime settings. They now persist only measured usage, derive compression
lines from current Runtime and model settings, and normalize legacy snapshots
when loading them.

The static website now uses the project GitHub Pages canonical URL and includes
a validated Pages deployment workflow.

Release note: 优化设置中心和 Agent Runtime 配置流程，避免重复标题、重复保存和未保存定制丢失；压缩线会随当前设置即时更新，官网也可通过 GitHub Pages 自动部署。

.github/workflows/pages.yml

@@ -0,0 +1,47 @@
+name: Deploy website to GitHub Pages
+
+on:
+  workflow_dispatch:
+  push:
+    branches:
+      - main
+    paths:
+      - 'sites/**'
+      - '.github/workflows/pages.yml'
+
+permissions:
+  contents: read
+  pages: write
+  id-token: write
+
+concurrency:
+  group: pages
+  cancel-in-progress: true
+
+jobs:
+  deploy:
+    name: Deploy static website
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+    runs-on: ubuntu-24.04
+
+    steps:
+      - uses: actions/checkout@v7
+
+      - name: Validate website
+        run: |
+          node sites/scripts/validate.mjs
+          node --check sites/app.js
+
+      - name: Configure GitHub Pages
+        uses: actions/configure-pages@v5
+
+      - name: Upload website artifact
+        uses: actions/upload-pages-artifact@v4
+        with:
+          path: sites
+
+      - name: Deploy website
+        id: deployment
+        uses: actions/deploy-pages@v4