feat(analytics): enable Google Analytics 4 via docs.json integrations.ga4

[GigaHierz]

The hole, and the fix

docs.json had no analytics configuration at all ("integrations" in docs.json → false at bdf40b37; grep for ga4|gtm|googleAnalytics|posthog|amplitude|mixpanel|segment|plausible|fathom → 0 hits), so page analytics were lost when the Mintlify plan changed. This adds Mintlify's documented GA4 block:

"integrations": { "ga4": { "measurementId": "G-0CXEKQ81V2" } }

The measurement ID is not new: G-0CXEKQ81V2 was the docs' GA4 property in docusaurus.config.js from 2021-09-21 (c931a1bf) until the Docusaurus removal on 2025-09-17 (b555aecb). Reusing it keeps the historical series in one property instead of starting a new one. (An older ID G-W2H8BZBELD existed for one month in 2021-08 and was replaced; not used here.)

What this does NOT do / residual risk

• Does not create a GA account or verify who currently administers property G-0CXEKQ81V2. If nobody on the team can access it any more, this ships events into a property we can't read — the ops box below is the check.
• Does not add GTM, consent banners or dashboards.
• No change to content or navigation: 5-line insertion, 0 deletions.

Judgement calls

• Reuse the historical property instead of creating a new one (the issue said "create a GA4 property"). Reasoning: continuity with 4 years of data; zero-cost to reverse — one-line ID swap if the team prefers a fresh property.

Issues

Refs #2249 — closes the code box (integrations.ga4.measurementId added). Still open: GA account ownership confirmed/shared with the DevRel team; Realtime verification after deploy; owner recorded.

Stacking / conflicts

Branched off main, independent of my other open PRs. Touches docs.json top-level only (lines 10–15); no overlap with navigation edits.

Verification evidence

$ python3 -c "import json;d=json.load(open('docs.json'));print(d['integrations'])"
{'ga4': {'measurementId': 'G-0CXEKQ81V2'}}
$ git diff --stat
 docs.json | 5 +++++
$ git log --all -S'G-0CXEKQ81V2' --format='%h %as %s' -- docusaurus.config.js
b555aecb 2025-09-17 remove: removed docusaurus (#2040)
c931a1bf 2021-09-21 Add Google Analytics (#121)

mint broken-links output is pasted in the first comment (run on this head). There is no test seam for a config key in a static-docs repo; mutation testing does not apply — the real check is GA4 Realtime after the preview/production deploy.

Remaining ops steps

• Confirm a team member can open GA4 property G-0CXEKQ81V2 (Admin → Property details) and share access with the DevRel team; if access is lost, create a new property and swap the ID
• After deploy, open GA4 Realtime and confirm hits from docs.celo.org
• Record the account owner in task: Add Google Analytics (GA4) to docs.json #2249

Checklist

• Title is the commit message I want on main
• docs.json parses; mint broken-links run on this head
• Judgement calls flagged above
• No secrets in the diff (a GA measurement ID is public by design — it ships in page HTML)
• Questions for the maintainer: do we still own G-0CXEKQ81V2? If not, say so and I'll swap in the new ID.

[GigaHierz]

mint broken-links on this head (5d09092), run in a clean detached worktree:

success no broken links found