Content Guidelines AI: mark Automattician traffic in Tracks events (#51280)

Every Tracks event this feature records now carries an is_a11n property, so
internal testing can be filtered out of product reporting. The feature is new
and low-volume, where a fortnight of internal clicking is a visible share of
the totals and there is no way to remove it after the fact.

Adds Status\Visitor::is_tracking_automattician(), using the three signals
settled on in #51217: an identified Automattician on WordPress.com Simple, and
A8C-proxied requests on Simple and WoA. It sits next to the existing
is_automattician_feature_flags_only() and delegates to it for the WoA case.

Putting it in jetpack-status rather than the plugin matters: the package is
autoloaded everywhere Jetpack runs, including on WordPress.com Simple where
extensions load through wpcom's own loader and load-jetpack.php never runs. So
Image Studio can use it too, which drops the duplicate copy of this logic it
was carrying.

The flag is attached in the feature's Tracks wrapper rather than at each call
site, so new events pick it up without anyone remembering to add it.

Co-authored-by: Claude Opus 5 <noreply@anthropic.com>

Committed via a GitHub action: https://github.com/Automattic/jetpack/actions/runs/31999471128

Upstream-Ref: Automattic/jetpack@e685714

Author: aagam-shah

composer.json

@@ -9,7 +9,7 @@
 		"automattic/jetpack-connection": "^8.10.3",
 		"automattic/jetpack-constants": "^3.0.12",
 		"automattic/jetpack-external-connections": "^0.1.39",
-		"automattic/jetpack-status": "^6.3.2-alpha"
+		"automattic/jetpack-status": "^6.4.0-alpha"
 	},
 	"require-dev": {
 		"yoast/phpunit-polyfills": "^4.0.0",