feat: Add more inspection events

[ellisong]

Adds new inspection events to the agent. These events include the drain event, window lifecycle events such as navigate, load, DOMContentLoaded, and the session event which emits on changes to the agent's session state.

Overview

Adds new inspection events to the agent. These are new events not originally outlined in the CDD. The 'origin' event mentioned in the JIRA ticket is excluded due to too much code effort and not enough of a use case to have it.

drain event: Emits when the agent drains for a particular feature

{
    agentIdentifier,
    type: 'lifecycle',
    name: 'drain',
    feature: group
}

window lifecycle events:

{
    timeStamp: evt.timeStamp,
    loaded: evt.target.document.readyState === 'complete',
    type: 'window',
    name: 'navigate' | 'load' | 'DOMContentLoaded'
    data: evt.target.location + ''
}

session event: Emits when the agent's session state changes

{
    agentIdentifier,
    type: 'lifecycle',
    name: 'session',
    feature: undefined,
    data: <session state>
}

Related Issue(s)

JIRA: https://new-relic.atlassian.net/browse/NR-377594
Follow-up ticket: https://new-relic.atlassian.net/browse/NR-375666

Testing

The inspection-events tests were expanded. Open the inspection-events.html in the test server to test locally.

Make sure tests pass for this PR.

[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	24.97 kB / 9.47 kB (gzip)	25.55 kB / 9.65 kB (gzip)	2.35% / 1.88% (gzip)
lite	async-chunk	52.6 kB / 17.45 kB (gzip)	52.6 kB / 17.45 kB (gzip)	0% / 0% (gzip)
pro	loader	52.91 kB / 18.61 kB (gzip)	53.49 kB / 18.79 kB (gzip)	1.09% / 0.96% (gzip)
pro	async-chunk	92 kB / 28.52 kB (gzip)	92 kB / 28.52 kB (gzip)	0% / 0% (gzip)
spa	loader	61.66 kB / 21.31 kB (gzip)	62.25 kB / 21.49 kB (gzip)	0.94% / 0.85% (gzip)
spa	async-chunk	116.63 kB / 35.49 kB (gzip)	116.63 kB / 35.49 kB (gzip)	0% / 0% (gzip)

[github-actions]

Last ran on June 10, 2025 18:43:31 CDT
Checking merge of (b17c046) into main (375c37f)

[codecov]

Codecov Report

Attention: Patch coverage is 88.23529% with 2 lines in your changes missing coverage. Please review.

Project coverage is 87.64%. Comparing base (375c37f) to head (b17c046).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
src/common/window/load.js	66.66%	1 Missing ⚠️
src/features/page_view_event/instrument/index.js	92.30%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1494      +/-   ##
==========================================
+ Coverage   87.61%   87.64%   +0.02%     
==========================================
  Files         197      197              
  Lines        7761     7778      +17     
  Branches     1563     1565       +2     
==========================================
+ Hits         6800     6817      +17     
- Misses        826      827       +1     
+ Partials      135      134       -1     

Flag	Coverage Δ
unit-tests	78.78% <88.23%> (+0.06%)	⬆️

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[ptang-nr]

LGTM