feat(ensapi): add openapi

[stevedylandev]

This PR starts implementation of hono-openapi to complete #1115. Work includes:

• Installing hono-openapi
• Updates validate.ts to use validator from hono-openapi
• Adds response zod schemas to ensnode-sdk
• Adds describeRoute to resolution endpoints
• Adds GET /openapi.json route

The result is an OpenAPI schema that can be fetched from /openapi.json from the ENSApi:

curl http://localhost:4334/openapi.json | jq . 

With the schema we can build new documentation that accepts OpenAPI for automatic API references. At least for the API we can write almost all of the documentation inside the routes themselves. Here is an example:

app.get(
  "/records/:name",
  describeRoute({
    summary: "Resolve ENS Records",
    description: `Resolves ENS records for a given name, including addresses, text records, and other metadata.

## Query Parameters

- \`addresses\` - Comma-separated list of coin type IDs (e.g., \`60\` for ETH, \`0\` for BTC)
- \`texts\` - Comma-separated list of text record keys (e.g., \`avatar\`, \`com.twitter\`)
- \`name\` - Set to \`true\` to include name resolution
- \`trace\` - Set to \`true\` to include resolution trace information
- \`accelerate\` - Set to \`true\` to attempt real-time acceleration

## Examples

### Resolve address records (ETH and BTC)
\`\`\`
GET /records/example.eth?addresses=60,0
\`\`\`

### Resolve text records (avatar and Twitter)
\`\`\`
GET /records/example.eth?texts=avatar,com.twitter
\`\`\`

### Combined resolution
\`\`\`
GET /records/example.eth?name=true&addresses=60,0&texts=avatar,com.twitter
\`\`\``,
    responses: {
      200: {
        description: "Successfully resolved records",
        content: {
          "application/json": {
            schema: resolver(makeResolveRecordsResponseSchema()),
          },
        },
      },
    },
  }),

Note

I don't like escaping characters in the mark up so I will be looking into another way to do this

This results in a docs page like this:

Take a look at the current preview built in a separate repo: https://docs-sepia-eight.vercel.app/docs/getApiResolveRecords

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Project	Deployment	Review	Updated (UTC)
admin.ensnode.io	Ready	Preview, Comment	Dec 23, 2025 9:51pm
ensnode.io	Ready	Preview, Comment	Dec 23, 2025 9:51pm
ensrainbow.io	Ready	Preview, Comment	Dec 23, 2025 9:51pm

[lightwalker-eth]

@stevedylandev This looks like an exciting direction to me. Appreciate your advice on next steps 👍