fix(config): normalize route rules with leading slash

[gioboa]

🔗 Linked issue

Fixes: #2463

❓ Type of change

• 📖 Documentation (updates to the documentation, readme, or JSdoc annotations)
• 🐞 Bug fix (a non-breaking change that fixes an issue)
• 👌 Enhancement (improving an existing functionality like performance)
• ✨ New feature (a non-breaking change that adds functionality)
• 🧹 Chore (updates to the build process or auxiliary tools and libraries)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

Vercel deployment is failing because with this configuration 👇 the .vercel/output/config.json is wrong.

//https://nitro.unjs.io/config
export default defineNitroConfig({
  compatibilityDate: "2025-01-07",
  srcDir: "server",
  routeRules: { "**": { headers: { "x-foo": "bar" } } },
  preset: 'vercel'
});

Forcing the initial / will solve the issue.

BEFORE ❌

FILE: .vercel/output/config.json

{
  "version": 3,
  "overrides": {},
  "routes": [
    {
      "headers": {
        "x-foo": "bar"
      },
      "src": "**"
    },
    {
      "handle": "filesystem"
    },
    {
      "src": "/(.*)",
      "dest": "/__nitro"
    }
  ]
}

AFTER ✅

FILE: .vercel/output/config.json

{
  "version": 3,
  "overrides": {},
  "routes": [
    {
      "headers": {
        "x-foo": "bar"
      },
      "src": "/(.*)"
    },
    {
      "handle": "filesystem"
    },
    {
      "src": "/(.*)",
      "dest": "/__nitro"
    }
  ]
}

📝 Checklist

• I have linked an issue or discussion.
• I have updated the documentation accordingly.

[pi0]

Can you please also update test/fixture/nitro.config with one route rule without leading slash? 🙏🏼

[pi0]

thnx!