feat: add @hono/markdown-for-agents middleware

[KKonstantinov]

Hono middleware for markdown-for-agents — converts HTML responses to clean, token-efficient Markdown when clients send Accept: text/markdown.

AI agents get ~80–90% token savings. Normal browser requests pass through untouched.

import { Hono } from 'hono'
import { markdown } from '@hono/markdown-for-agents'

const app = new Hono()
app.use(markdown())

app.get('/', (c) => {
  return c.html('<h1>Hello</h1>')
})

export default app

# Normal HTML response
curl http://localhost:3000

# Markdown response for AI agents
curl -H "Accept: text/markdown" http://localhost:3000

The response includes Content-Type: text/markdown, x-markdown-tokens, ETag, Vary: Accept, and optional content-signal / server-timing headers.

See the markdown-for-agents docs for full options and the playground.

The author should do the following, if applicable

• Add tests
• Run tests
• yarn changeset at the top of this repo and push the changeset
• Follow the contribution guide

[changeset-bot]

🦋 Changeset detected

Latest commit: 6810517

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@hono/markdown-for-agents	Minor

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR