feat: Support OpenFeature tracking

[kinyoklion]

Implements the OpenFeature tracking API in the Ruby provider so experimentation metric events reach LaunchDarkly.

• Adds Provider#track, mapping TrackingEventDetails#fields to the LD custom event data and #value to metric_value.
• A track call without an evaluation context logs a warning and sends nothing, since LaunchDarkly requires a context to associate the event with.
• Raises the openfeature-sdk floor to >= 0.6.1 (< 0.7.0); TrackingEventDetails and Client#track do not exist in 0.6.0.

Implementation details

Requirements

• I have added test coverage for new or changed functionality
• I have followed the repository's pull request submission guidelines
• I have validated my changes against all supported platform versions

Related issues

Part of an audit of the LaunchDarkly OpenFeature providers against the current OpenFeature specification. Tracking (spec section 6) was unimplemented here, and per spec 6.1.4 the OpenFeature SDK silently no-ops when a provider lacks track, so events were being dropped without any error.

Describe the solution you've provided

OpenFeature::SDK::Client#track forwards to provider.track(name, evaluation_context:, tracking_event_details:). The provider converts the evaluation context with the existing EvaluationContextConverter and calls LDClient#track(event_name, context, data, metric_value). Empty fields are normalized to nil so no empty hash is attached to the event.

Describe alternatives you've considered

Sending the event with an anonymous/placeholder context when no evaluation context is supplied — rejected, because it would attribute metric events to a context the application never used. Warning and dropping matches the behavior of the Python provider.

Testing

bundle exec rake (RSpec + RuboCop) on Ruby 3.4: 57 examples, 0 failures; 12 files inspected, no offenses. Ruby 3.4 was used because the gemspec requires >= 3.4.

@cursor review

Link to Devin session: https://app.devin.ai/sessions/0c452d209ec54b068ba120b4c92b8f6c
Requested by: @kinyoklion

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Note

Overview
Implements OpenFeature tracking on the Ruby provider so experiment metric events reach LaunchDarkly instead of being silently dropped.

Provider#track converts the evaluation context and maps TrackingEventDetails#fields to LD event data and #value to metric_value. Calls without a context log a warning and send nothing (LD requires a context). Empty fields are sent as nil.

Bumps openfeature-sdk from ~> 0.6.0 to ~> 0.6.1 because tracking types/APIs are not in 0.6.0. Specs cover context, details, and the no-context no-op.

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