chore: adapt to posthog-ios 4.0 reloadFeatureFlags callback

[turnipdabeets]

💡 Motivation and Context

Companion to PostHog/posthog-ios#913, stacked on #637. Spec: PostHog/sdk-specs#99.

posthog-ios 4.0 passes a PostHogFeatureFlagsLoaded to the reloadFeatureFlags(_:) callback, so the existing zero-argument closure no longer compiles. This changes it to { _ in ... }. Behavior is unchanged: the Dart Future still resolves once the native reload finishes.

Exposing errorsLoading to Dart is left for a follow-up; reloadFeatureFlags() stays Future<void>.

💚 How did you test it?

• Not built locally: the plugin requires posthog-ios >= 4.0.0, which isn't released yet. The posthog-ios side compiles with this closure shape (make buildSdk on #913).

📝 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

No changeset: internal change with no Dart API impact; it ships with #637.

🤖 Agent context

Autonomy: Human-driven (agent-assisted)

• Written with Claude Code (Opus 5.5). One-line mechanical change to follow the posthog-ios 4.0 signature.

🤖 Generated with Claude Code

[github-actions]

posthog-flutter Compliance Report

Date: 2026-10-07 00:36:02 UTC
Duration: 96728ms

✅ All Tests Passed!

45/45 tests passed

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Capture Tests

✅ 29/29 tests passed

View Details

Test	Status	Duration
Format Validation.Event Has Required Fields	✅	137ms
Format Validation.Event Has Uuid	✅	117ms
Format Validation.Event Has Lib Properties	✅	115ms
Format Validation.Distinct Id Is String	✅	114ms
Format Validation.Token Is Present	✅	116ms
Format Validation.Custom Properties Preserved	✅	116ms
Format Validation.Event Has Timestamp	✅	115ms
Retry Behavior.Retries On 503	✅	5331ms
Retry Behavior.Does Not Retry On 400	✅	2117ms
Retry Behavior.Does Not Retry On 401	✅	2118ms
Retry Behavior.Respects Retry After Header	✅	8125ms
Retry Behavior.Implements Backoff	✅	15434ms
Retry Behavior.Retries On 500	✅	5224ms
Retry Behavior.Retries On 502	✅	5226ms
Retry Behavior.Retries On 504	✅	5224ms
Retry Behavior.Max Retries Respected	✅	15446ms
Deduplication.Generates Unique Uuids	✅	122ms
Deduplication.Preserves Uuid On Retry	✅	5225ms
Deduplication.Preserves Uuid And Timestamp On Retry	✅	10335ms
Deduplication.Preserves Uuid And Timestamp On Batch Retry	✅	5230ms
Deduplication.No Duplicate Events In Batch	✅	122ms
Deduplication.Different Events Have Different Uuids	✅	116ms
Compression.Sends Gzip When Enabled	✅	116ms
Batch Format.Uses Proper Batch Structure	✅	113ms
Batch Format.Flush With No Events Sends Nothing	✅	109ms
Batch Format.Multiple Events Batched Together	✅	123ms
Error Handling.Does Not Retry On 403	✅	2115ms
Error Handling.Does Not Retry On 413	✅	2119ms
Error Handling.Retries On 408	✅	5224ms

Feature_Flags Tests

✅ 16/16 tests passed

View Details

Test	Status	Duration
Request Payload.Request With Person Properties Device Id	✅	13ms
Request Payload.Flags Request Uses V2 Query Param	✅	9ms
Request Payload.Flags Request Hits Flags Path Not Decide	✅	9ms
Request Payload.Flags Request Omits Authorization Header	✅	9ms
Request Payload.Token In Flags Body Matches Init	✅	8ms
Request Payload.Groups Round Trip	✅	9ms
Request Payload.Groups Default To Empty Object	✅	8ms
Request Payload.Person Properties Distinct Id Auto Populated When Caller Omits It	✅	9ms
Request Payload.Disable Geoip False Propagates As Geoip Disable False	✅	8ms
Request Payload.Disable Geoip Omitted Defaults To False	✅	8ms
Request Payload.Flag Keys To Evaluate Contains Only Requested Key	✅	9ms
Request Lifecycle.No Flags Request On Init Alone	✅	3ms
Request Lifecycle.No Flags Request On Normal Capture	✅	112ms
Request Lifecycle.Two Flag Calls Produce Two Remote Requests	✅	16ms
Request Lifecycle.Mock Response Value Is Returned To Caller	✅	8ms
Side Effect Events.Get Feature Flag Captures Feature Flag Called Event	✅	115ms