Standardize UI button labels and restructure index into two pages

- Use [**text**] bracket format for all UI button references across docs
- Split zh/index into beforestart and intro pages
- Update primary color to teal (#0d9488)
- Add JSON format reference link and misc text fixes

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

.claude/settings.local.json

@@ -1,7 +1,8 @@
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-      "WebSearch"
+      "WebSearch",
+      "WebFetch(domain:mintlify.com)"
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