Raise test coverage from 46% to 97% of lines

[loevgaard]

Fixes #32

Last in the series, stacked on #55.

Where it started

Classes:  6.90% (2/29)
Methods: 30.00% (21/70)
Lines:   45.91% (129/281)

Only two classes were fully covered, and most subscriber coverage came from getSubscribedEvents() being called during kernel boot rather than from behaviour being exercised. Nearly every bug this series fixed lived in that untested half.

Where it ends

Classes: 80.00% (28/35)
Methods: 90.91% (80/88)
Lines:   97.52% (472/484)

The earlier PRs covered what they changed. This one closes what was left: PopulateRequestPropertiesSubscriber, PopulatePixelsSubscriber, PopulateFbpAndFbcPropertiesSubscriber, ConsentChecker, AddEventToTagBagSubscriber, AddLibraryToTagBagSubscriber and StoreFbcSubscriber.

The end-to-end test

PipelineTest is the one this series needed most. It boots a real kernel with both sides enabled and a recording ClientInterface, pushes a request, registers an application listener at PRIORITY_ENRICH, dispatches a real ConversionsApiEventRaised, and then asserts on both ends:

• the command was dispatched, routed, handled and reached the client;
• the payload carries the source url, the user agent, an fbp, and the enriching listener's email as a SHA-256 hash;
• the tag bag holds the fbq('init') and fbq('track') calls, carrying the same eventID as the server payload, which is what makes Meta deduplicate the pair.

A second test sends a Googlebot user agent and asserts nothing reaches the client, nothing is rendered, and the application's enrichment listener was never invoked.

That test exercises the wiring between listeners, which is where a missing service argument or a bus that no longer exists actually shows up. It would have caught the very first issue in this series.

Keeping it there

codecov.yml turns coverage into a gate: 95% on the project with a 1% threshold, 90% on the patch. The coverage job already uploaded to Codecov but nothing consumed the result.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.49%. Comparing base (2b99b02) to head (029bb97).

Additional details and impacted files

@@             Coverage Diff              @@
##             master      #56      +/-   ##
============================================
+ Coverage     81.93%   90.49%   +8.56%     
+ Complexity      148      147       -1     
============================================
  Files            31       31              
  Lines           487      484       -3     
============================================
+ Hits            399      438      +39     
+ Misses           88       46      -42     

see 10 files with indirect coverage changes

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