feat(error-tracking): standardize exception event metadata

[hpouillot]

💡 Motivation and Context

Standardize PHP exception events across manual and automatic capture paths with the cross-SDK metadata contract, including severity, stable sources, mechanisms, deterministic linkage, and reserved property ownership.

Canonical contract: https://github.com/PostHog/sdk-specs/blob/main/openspec/specs/exception-event-metadata/spec.md

💚 How did you test it?

• Focused PHPUnit exception tests: 42 passed

📝 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 change to generate a change intent file

[github-actions]

posthog-php Compliance Report

Date: 2026-08-26 08:26:07 UTC
Duration: 95307ms

✅ All Tests Passed!

46/46 tests passed

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Capture Tests

✅ 29/29 tests passed

View Details

Test	Status	Duration
Format Validation.Event Has Required Fields	✅	12ms
Format Validation.Event Has Uuid	✅	6ms
Format Validation.Event Has Lib Properties	✅	6ms
Format Validation.Distinct Id Is String	✅	6ms
Format Validation.Token Is Present	✅	6ms
Format Validation.Custom Properties Preserved	✅	5ms
Format Validation.Event Has Timestamp	✅	6ms
Retry Behavior.Retries On 503	✅	5316ms
Retry Behavior.Does Not Retry On 400	✅	2009ms
Retry Behavior.Does Not Retry On 401	✅	2010ms
Retry Behavior.Respects Retry After Header	✅	8015ms
Retry Behavior.Implements Backoff	✅	15730ms
Retry Behavior.Retries On 500	✅	5115ms
Retry Behavior.Retries On 502	✅	5116ms
Retry Behavior.Retries On 504	✅	5115ms
Retry Behavior.Max Retries Respected	✅	16530ms
Deduplication.Generates Unique Uuids	✅	12ms
Deduplication.Preserves Uuid On Retry	✅	5114ms
Deduplication.Preserves Uuid And Timestamp On Retry	✅	10322ms
Deduplication.Preserves Uuid And Timestamp On Batch Retry	✅	5118ms
Deduplication.No Duplicate Events In Batch	✅	13ms
Deduplication.Different Events Have Different Uuids	✅	7ms
Compression.Sends Gzip When Enabled	✅	6ms
Batch Format.Uses Proper Batch Structure	✅	6ms
Batch Format.Flush With No Events Sends Nothing	✅	3ms
Batch Format.Multiple Events Batched Together	✅	11ms
Error Handling.Does Not Retry On 403	✅	2006ms
Error Handling.Does Not Retry On 413	✅	2010ms
Error Handling.Retries On 408	✅	5116ms

Feature_Flags Tests

✅ 17/17 tests passed

View Details

Test	Status	Duration
Request Payload.Request With Person Properties Device Id	✅	7ms
Request Payload.Flags Request Uses V2 Query Param	✅	5ms
Request Payload.Flags Request Hits Flags Path Not Decide	✅	4ms
Request Payload.Flags Request Omits Authorization Header	✅	5ms
Request Payload.Token In Flags Body Matches Init	✅	5ms
Request Payload.Groups Round Trip	✅	5ms
Request Payload.Groups Default To Empty Object	✅	4ms
Request Payload.Disable Geoip False Propagates As Geoip Disable False	✅	5ms
Request Payload.Disable Geoip Omitted Defaults To False	✅	5ms
Request Payload.Flag Keys To Evaluate Contains Only Requested Key	✅	4ms
Request Lifecycle.No Flags Request On Init Alone	✅	2ms
Request Lifecycle.No Flags Request On Normal Capture	✅	6ms
Request Lifecycle.Two Flag Calls Produce Two Remote Requests	✅	7ms
Request Lifecycle.Mock Response Value Is Returned To Caller	✅	5ms
Retry Behavior.Retries Flags On 502	✅	108ms
Retry Behavior.Retries Flags On 504	✅	108ms
Side Effect Events.Get Feature Flag Captures Feature Flag Called Event	✅	8ms