fix(docs): deduplicate page headings

Author: onmax

docs/content/1.guide/1.index.md

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+title: Getting Started
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-# Getting Started
-
 Validate your Nuxt runtime config at build or runtime using **Zod**, **Valibot**, **ArkType**, or any [Standard Schema](https://standardschema.dev/) compatible library.
 
 ## Features

docs/content/1.guide/2.configuration.md

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+title: Configuration
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-# Configuration
-
 All options for `safeRuntimeConfig` in your `nuxt.config.ts`.
 
 ## Options Reference

docs/content/1.guide/3.type-safety.md

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+title: Type Safety
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-# Type Safety
-
 The module generates TypeScript types from your schema, making `useSafeRuntimeConfig()` fully typed without manual generics in both app and server code.
 
 ## How It Works

docs/content/1.guide/4.validation.md

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+title: Validation
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-# Validation
-
 The module validates your runtime config to catch configuration errors early. By default, validation runs at build time only.
 
 ## Build-time Validation (Default)

docs/content/2.schemas/1.index.md

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+title: Schema Libraries
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-# Schema Libraries
-
 This module works with any [Standard Schema](https://standardschema.dev/) compatible library. Standard Schema is a shared interface that lets validation libraries work interchangeably.
 
 ## Supported Libraries

docs/content/2.schemas/2.valibot.md

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+title: Valibot
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-# Valibot
-
 [Valibot](https://valibot.dev/) is a modular validation library with excellent tree-shaking. Only the functions you use are bundled.
 
 ## Installation

docs/content/2.schemas/3.zod.md

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+title: Zod
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-# Zod
-
 [Zod](https://zod.dev/) is a TypeScript-first schema validation library with a fluent API.
 
 ## Installation

docs/content/2.schemas/4.arktype.md

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+title: ArkType
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-# ArkType
-
 [ArkType](https://arktype.io/) is a type-first validation library where you write types that look like TypeScript syntax.
 
 ## Installation

docs/content/3.integrations/1.index.md

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+title: Integrations
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-# Integrations
-
 Extend the module with additional capabilities.
 
 ## Available Integrations

docs/content/3.integrations/2.shelve.md

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+title: Shelve Integration
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-# Shelve Integration
-
 [Shelve](https://shelve.cloud) is a secrets management platform for development teams. This integration fetches your secrets at build time and injects them into runtime config.
 
 :u-button{to="https://shelve.cloud/docs/getting-started" label="Shelve Documentation" target="_blank" trailing-icon="i-ph-arrow-square-out"}