feat: Set up framework for detecting AJAX calls from MFEs

[metal-messiah]

Adds capability to detect a custom header for detecting MFE-linked AJAX traffic. This is in support of a future initiative and the specifics may change over time as the feature approaches GA.

Overview

Related Issue(s)

Testing

[github-actions]

Supportability Metric Usage Changes:

No matching changes found

Supportability Metrics .md File Changes:

supportability_metrics.md was changed? false

New supportability metrics require changes to supportability_metrics.md, as well as a new PR to Angler. Please ensure an Angler PR is created and linked to this PR.

[github-actions]

Asset Size Report

Merging this pull request will result in the following asset size changes:

Agent	Asset	Previous Size	New Size	Diff
lite	loader	27.03 kB / 10.22 kB (gzip)	27.03 kB / 10.23 kB (gzip)	0% / 0.02% (gzip)
lite	async-chunk	55.11 kB / 18.48 kB (gzip)	55.16 kB / 18.5 kB (gzip)	0.1% / 0.14% (gzip)
pro	loader	60.04 kB / 20.97 kB (gzip)	60.76 kB / 21.22 kB (gzip)	1.2% / 1.17% (gzip)
pro	async-chunk	91.96 kB / 29.22 kB (gzip)	92.22 kB / 29.31 kB (gzip)	0.28% / 0.33% (gzip)
spa	loader	62.44 kB / 21.79 kB (gzip)	63.16 kB / 22.03 kB (gzip)	1.15% / 1.09% (gzip)
spa	async-chunk	103.18 kB / 32.1 kB (gzip)	103.44 kB / 32.19 kB (gzip)	0.25% / 0.29% (gzip)

[codecov]

Codecov Report

❌ Patch coverage is 53.48837% with 20 lines in your changes missing coverage. Please review.
✅ Project coverage is 88.24%. Comparing base (81ed082) to head (61cb20b).

Files with missing lines	Patch %	Lines
src/common/wrap/wrap-fetch.js	28.57%	5 Missing and 5 partials ⚠️
src/common/util/v2.js	0.00%	3 Missing and 1 partial ⚠️
src/common/wrap/wrap-xhr.js	55.55%	4 Missing ⚠️
src/features/ajax/aggregate/index.js	81.81%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1612      +/-   ##
==========================================
- Coverage   88.44%   88.24%   -0.20%     
==========================================
  Files         208      208              
  Lines        7869     7906      +37     
  Branches     1625     1640      +15     
==========================================
+ Hits         6960     6977      +17     
- Misses        800      814      +14     
- Partials      109      115       +6     

Flag	Coverage Δ
unit-tests	81.96% <53.48%> (-0.24%)	⬇️

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[github-actions]

Last ran on February 09, 2026 08:34:47 CST
Checking merge of (61cb20b) into main (81ed082)

[metal-messiah]

This PR will have lots of merge conflicts between soft nav changes and deregister API, so waiting until those are merged to do any further changes here