Integer type matcher is unanchored, so cellpadding="6px" (and "abc5") pass validation

Describe the bug

cellpadding and cellspacing are declared as integer, but the integer type matcher is unanchored /\d+/. Any string that contains a digit is treated as valid, including cellpadding="6px" and cellpadding="abc5".

The value is then copied unchanged onto the HTML <table>. cellpadding / cellspacing are HTML attributes that take a non-negative integer (pixels), not a CSS length. "6px" is invalid HTML; some email clients ignore it and you get no padding.

To Reproduce

<mjml>
  <mj-body>
    <mj-section>
      <mj-column>
        <mj-table cellpadding="6px" cellspacing="2px">
          <tr><td>x</td></tr>
        </mj-table>
      </mj-column>
    </mj-section>
  </mj-body>
</mjml>

const mjml2html = require('mjml')
const { html, errors } = mjml2html(mjml)
console.log(errors)
// look for cellpadding="6px" in html

Also valid today, which should not be:

<mj-table cellpadding="abc5">

Expected behavior

A valid-types error, matching the documented type (integer) and the HTML attribute:

Attribute cellpadding has invalid value: 6px for type Integer

Bare integers (cellpadding="6") should still pass.

MJML environment

• MJML Version: current master (also 4.x)
• MJML tool used: Node mjml CLI / mjml2html

Email sending environment

N/A — this is a validator bug. The rendering risk is that "6px" is emitted as-is.

Affected email clients

N/A for the validator miss. Outlook’s Word engine and other strict parsers can ignore cellpadding="6px" entirely.

Additional context

Root cause is the integer matcher:

// packages/mjml-core/src/types/integer.js
this.matchers = [/\d+/]

String.prototype.search / the type isValid() path only needs a digit somewhere in the value.

Suggested fix: anchor it, e.g. /^\d+$/. That matches the docs, HTML4/HTML5 (cellpadding is a non-negative integer), and what email clients actually honor.

mj-table cellpadding / cellspacing look like the only integer attributes, so the blast radius is small. Existing templates that compile cleanly with "6px" would start getting a validation error — which is the point.