Add mm_attribution capture on Agent Wallet docs

[hieu-w]

Description

Park last-touch UTMs and ad click IDs from /agent-wallet docs landings (including the quickstart) in the shared mm_attribution cookie (Domain=.metamask.io). This matches metamask.io so a later sign-in on developer.metamask.io can still attribute the campaign.

• Only writes when the path includes /agent-wallet and the URL has at least one whitelisted UTM or click ID (utm_source, utm_medium, utm_campaign, utm_term, utm_content, plus gclid / twclid / fbclid / msclkid / ttclid / li_fat_id)
• Last-touch merge: new URL params take the 10-key budget first; leftover slots keep earlier tags so a UTM-only visit does not drop a prior gclid
• Sanitizes and caps keys/values to the same limits as the developer dashboard reader and backend
• Cookie: 90 days, Secure, SameSite=Lax

This is site JS, not a documentation content change.

Issue(s) fixed

N/A

Preview

• Agent Wallet quickstart

To verify: open the preview with ?utm_source=google&utm_medium=cpc&gclid=abc and confirm mm_attribution is set for .metamask.io. Localhost will not keep the cookie because of the shared domain.

Checklist

• If this PR updates or adds documentation content that changes or adds technical meaning, it has received an approval from an engineer or DevRel from the relevant team.
• If this PR updates or adds documentation content, it has received an approval from a technical writer.

External contributor checklist

• I've read the contribution guidelines.
• I've created a new issue (or assigned myself to an existing issue) describing what this PR addresses.

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Note

Medium Risk
Writes a cross-subdomain tracking cookie with user-supplied query params; mitigated by whitelisting, sanitization, and size limits aligned with server-side attribution handling.

Overview
Adds last-touch marketing attribution on Agent Wallet doc landings so UTM and ad click IDs from the query string are stored in the shared mm_attribution cookie for developer.metamask.io to read later.

A new Docusaurus client module runs on route changes (skipping no-op navigations) and calls writeAttributionCookie, which only runs on paths containing /agent-wallet when at least one whitelisted UTM or click ID is present. The writer sanitizes and caps keys/values to match the developer dashboard and backend limits, merges with an existing cookie so new URL params win without dropping unrelated prior click IDs, sets Domain=.metamask.io, 90-day expiry, and Secure / SameSite=Lax. docusaurus.config.js registers the module alongside the existing scroll-fix client script.

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Project	Deployment	Actions	Updated
metamask-docs	Ready	Preview	Sep 15, 2026 11:34am UTC