fix: require safe Req versions

[dustinbyrne]

💡 Motivation and Context

Req has security fixes available in the 0.6 line:

• https://nvd.nist.gov/vuln/detail/CVE-2026-49756
• https://nvd.nist.gov/vuln/detail/CVE-2026-49755

The SDK dependency constraint still allowed affected Req releases. This tightens the minimum to >= 0.6.1 while preserving the previous < 1.0.0 upper bound, so downstream projects resolve to a fixed Req version without narrowing future compatible 0.x releases unnecessarily.

Also adds a patch Sampo changeset for the release notes.

💚 How did you test it?

• mix deps.get
• mix test
• mix format --check-formatted
• mix compile --warnings-as-errors && mix posthog.public_api --check
• mix credo --strict
• mix hex.build

📝 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 sampo add to generate a changeset file

🤖 Agent context

Autonomy: Human-driven (agent-assisted)

Pi made the scoped dependency metadata change and generated the Sampo changeset. A reviewer subagent checked the diff; based on that review, the lockfile was left unchanged because it already uses Req 0.6.1 and extra transitive dependency churn was unnecessary.

[greptile-apps]

_{Reviews (1): Last reviewed commit: "fix: require safe Req versions" | Re-trigger Greptile}

[github-actions]

posthog-elixir Compliance Report

Date: 2026-07-08 19:16:59 UTC
Duration: 117702ms

✅ All Tests Passed!

46/46 tests passed

---

Capture Tests

✅ 29/29 tests passed

View Details

Test	Status	Duration
Format Validation.Event Has Required Fields	✅	610ms
Format Validation.Event Has Uuid	✅	611ms
Format Validation.Event Has Lib Properties	✅	611ms
Format Validation.Distinct Id Is String	✅	610ms
Format Validation.Token Is Present	✅	610ms
Format Validation.Custom Properties Preserved	✅	610ms
Format Validation.Event Has Timestamp	✅	610ms
Retry Behavior.Retries On 503	✅	5616ms
Retry Behavior.Does Not Retry On 400	✅	2613ms
Retry Behavior.Does Not Retry On 401	✅	2613ms
Retry Behavior.Respects Retry After Header	✅	5616ms
Retry Behavior.Implements Backoff	✅	15614ms
Retry Behavior.Retries On 500	✅	5616ms
Retry Behavior.Retries On 502	✅	5616ms
Retry Behavior.Retries On 504	✅	5616ms
Retry Behavior.Max Retries Respected	✅	15627ms
Deduplication.Generates Unique Uuids	✅	624ms
Deduplication.Preserves Uuid On Retry	✅	5616ms
Deduplication.Preserves Uuid And Timestamp On Retry	✅	10622ms
Deduplication.Preserves Uuid And Timestamp On Batch Retry	✅	5619ms
Deduplication.No Duplicate Events In Batch	✅	617ms
Deduplication.Different Events Have Different Uuids	✅	614ms
Compression.Sends Gzip When Enabled	✅	611ms
Batch Format.Uses Proper Batch Structure	✅	611ms
Batch Format.Flush With No Events Sends Nothing	✅	607ms
Batch Format.Multiple Events Batched Together	✅	615ms
Error Handling.Does Not Retry On 403	✅	2613ms
Error Handling.Does Not Retry On 413	✅	2614ms
Error Handling.Retries On 408	✅	5617ms

Feature_Flags Tests

✅ 17/17 tests passed

View Details

Test	Status	Duration
Request Payload.Request With Person Properties Device Id	✅	611ms
Request Payload.Flags Request Uses V2 Query Param	✅	611ms
Request Payload.Flags Request Hits Flags Path Not Decide	✅	610ms
Request Payload.Flags Request Omits Authorization Header	✅	610ms
Request Payload.Token In Flags Body Matches Init	✅	609ms
Request Payload.Groups Round Trip	✅	610ms
Request Payload.Groups Default To Empty Object	✅	610ms
Request Payload.Disable Geoip False Propagates As Geoip Disable False	✅	610ms
Request Payload.Disable Geoip Omitted Defaults To False	✅	610ms
Request Payload.Flag Keys To Evaluate Contains Only Requested Key	✅	610ms
Request Lifecycle.No Flags Request On Init Alone	✅	4ms
Request Lifecycle.No Flags Request On Normal Capture	✅	609ms
Request Lifecycle.Two Flag Calls Produce Two Remote Requests	✅	1216ms
Request Lifecycle.Mock Response Value Is Returned To Caller	✅	611ms
Retry Behavior.Retries Flags On 502	✅	912ms
Retry Behavior.Retries Flags On 504	✅	914ms
Side Effect Events.Get Feature Flag Captures Feature Flag Called Event	✅	1214ms