fix(rails): dedupe ActiveJob exception captures

[marandaneto]

💡 Motivation and Context

Fixes #217.

When both Rails exception auto-capture and ActiveJob instrumentation are enabled, a failing job can be captured once by ActiveJobExtensions and again when Rails reports the same re-raised exception through Rails.error with source application.active_support.

This PR marks exceptions successfully captured by the ActiveJob integration and has the Rails error subscriber skip only those already-captured exceptions. Unmarked application.active_support reports continue to be captured normally.

💚 How did you test it?

• BUNDLE_PATH=/Users/marandaneto/Github/posthog-ruby/vendor/bundle bundle exec rspec --format doc spec/posthog/rails/exception_mechanism_spec.rb
• BUNDLE_PATH=/Users/marandaneto/Github/posthog-ruby/vendor/bundle bundle exec rubocop posthog-rails/lib/posthog/rails.rb posthog-rails/lib/posthog/rails/active_job.rb posthog-rails/lib/posthog/rails/error_subscriber.rb spec/posthog/rails/exception_mechanism_spec.rb

📝 Checklist

• I reviewed the submitted code.
• I added tests to verify the changes.
• I updated the docs if needed.
• No breaking change or entry added to the changelog.

If releasing new changes

• Ran pnpm changeset to generate a changeset file

🤖 Agent context

Autonomy: Human-driven (agent-assisted)

Implemented with pi. I chose an exception-level marker instead of skipping all application.active_support reports so unrelated Rails error reports are not suppressed. The tests cover the duplicate ActiveJob path and confirm unmarked ActiveSupport reports still pass through the Rails error subscriber.

[github-actions]

posthog-ruby Compliance Report

Date: 2026-07-05 07:21:46 UTC
Duration: 98568ms

✅ All Tests Passed!

46/46 tests passed

---

Capture Tests

✅ 29/29 tests passed

View Details

Test	Status	Duration
Format Validation.Event Has Required Fields	✅	109ms
Format Validation.Event Has Uuid	✅	107ms
Format Validation.Event Has Lib Properties	✅	109ms
Format Validation.Distinct Id Is String	✅	107ms
Format Validation.Token Is Present	✅	107ms
Format Validation.Custom Properties Preserved	✅	107ms
Format Validation.Event Has Timestamp	✅	108ms
Retry Behavior.Retries On 503	✅	5314ms
Retry Behavior.Does Not Retry On 400	✅	2109ms
Retry Behavior.Does Not Retry On 401	✅	2109ms
Retry Behavior.Respects Retry After Header	✅	8116ms
Retry Behavior.Implements Backoff	✅	15722ms
Retry Behavior.Retries On 500	✅	5213ms
Retry Behavior.Retries On 502	✅	5212ms
Retry Behavior.Retries On 504	✅	5212ms
Retry Behavior.Max Retries Respected	✅	15717ms
Deduplication.Generates Unique Uuids	✅	111ms
Deduplication.Preserves Uuid On Retry	✅	5213ms
Deduplication.Preserves Uuid And Timestamp On Retry	✅	10319ms
Deduplication.Preserves Uuid And Timestamp On Batch Retry	✅	5215ms
Deduplication.No Duplicate Events In Batch	✅	111ms
Deduplication.Different Events Have Different Uuids	✅	107ms
Compression.Sends Gzip When Enabled	✅	107ms
Batch Format.Uses Proper Batch Structure	✅	107ms
Batch Format.Flush With No Events Sends Nothing	✅	4ms
Batch Format.Multiple Events Batched Together	✅	110ms
Error Handling.Does Not Retry On 403	✅	2109ms
Error Handling.Does Not Retry On 413	✅	2108ms
Error Handling.Retries On 408	✅	5212ms

Feature_Flags Tests

✅ 17/17 tests passed

View Details

Test	Status	Duration
Request Payload.Request With Person Properties Device Id	✅	109ms
Request Payload.Flags Request Uses V2 Query Param	✅	109ms
Request Payload.Flags Request Hits Flags Path Not Decide	✅	109ms
Request Payload.Flags Request Omits Authorization Header	✅	107ms
Request Payload.Token In Flags Body Matches Init	✅	107ms
Request Payload.Groups Round Trip	✅	107ms
Request Payload.Groups Default To Empty Object	✅	107ms
Request Payload.Disable Geoip False Propagates As Geoip Disable False	✅	107ms
Request Payload.Disable Geoip Omitted Defaults To False	✅	107ms
Request Payload.Flag Keys To Evaluate Contains Only Requested Key	✅	107ms
Request Lifecycle.No Flags Request On Init Alone	✅	3ms
Request Lifecycle.No Flags Request On Normal Capture	✅	106ms
Request Lifecycle.Two Flag Calls Produce Two Remote Requests	✅	111ms
Request Lifecycle.Mock Response Value Is Returned To Caller	✅	106ms
Retry Behavior.Retries Flags On 502	✅	236ms
Retry Behavior.Retries Flags On 504	✅	246ms
Side Effect Events.Get Feature Flag Captures Feature Flag Called Event	✅	109ms

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