chore(openfeature): pin mixpanel-ruby ~> 3.3 for fallback_reason (SDK-126)

[tylerjroach]

⚠️ DO NOT MERGE — intentionally red CI

Bundler will refuse to resolve mixpanel-ruby ~> 3.3 until that version exists on RubyGems. That failure is the point of this PR — it enforces the correct two-step release sequencing.

Summary

• Bump openfeature-provider/mixpanel-ruby-openfeature.gemspec runtime dep: ~> 3.1 → ~> 3.3.
• Bump mixpanel-ruby-openfeature version: 0.1.0 → 0.2.0.
• Add openfeature/v0.2.0 CHANGELOG entry.

Why

The wrapper's openfeature-provider/lib/mixpanel/openfeature/provider.rb:81 dispatches on SelectedVariant#fallback_reason, which was introduced by the SDK-79 merge in #153. Both published mixpanel-ruby versions in the previous ~> 3.1 range — 3.1.0 and 3.2.0 — predate SDK-79 and lack fallback_reason. Any install that paired mixpanel-ruby-openfeature 0.1.0 with those would raise NoMethodError on every evaluation past the existing rescue StandardError block. Greptile caught this on #153 immediately post-merge.

Release sequencing

1. This PR (now): red on CI because mixpanel-ruby ~> 3.3 isn't published.
2. Release mixpanel-ruby 3.3.0 with the SDK-79 changes:
   • Bump lib/mixpanel-ruby/version.rb → 3.3.0 on master
   • Cut the RubyGems release via the existing release-rubygems.yml workflow
3. This PR flips green → merge + cut mixpanel-ruby-openfeature 0.2.0.

Verified locally

bundle install in openfeature-provider/:

Could not find compatible versions
Because mixpanel-ruby >= 3.3, < 4.A could not be found in source at `..`
and every version of mixpanel-ruby-openfeature depends on mixpanel-ruby ~> 3.3,
  mixpanel-ruby-openfeature cannot be used.

Exactly the error CI should produce.

Linear: SDK-126

[linear-code]

SDK-126

[greptile-apps]

Confidence Score: 4/5

The changelog header can omit the release notes from the GitHub release.

• The dependency constraint matches the required SDK API.
• The provider version matches the planned tag.
• Direct tagging cannot extract the new changelog section.

openfeature-provider/CHANGELOG.md

Important Files Changed

Filename	Overview
openfeature-provider/CHANGELOG.md	Adds 0.2.0 release notes, but the header does not match the release workflow's extraction format.
openfeature-provider/lib/mixpanel/openfeature/version.rb	Updates the provider version from 0.1.0 to 0.2.0.
openfeature-provider/mixpanel-ruby-openfeature.gemspec	Requires the SDK release that provides fallback_reason.

_{Reviews (1): Last reviewed commit: "release(openfeature): pin mixpanel-ruby ..." | Re-trigger Greptile}

[greptile-apps]

Release Notes Section Is Skipped

When openfeature/v0.2.0 is tagged directly, the release workflow searches for a ## [openfeature/v0.2.0] header. This unbracketed header does not match, so the GitHub release receives placeholder text instead of these notes.

Suggested change

	## openfeature/v0.2.0
	## [openfeature/v0.2.0](https://github.com/mixpanel/mixpanel-ruby/tree/openfeature/v0.2.0)

Context Used: Our developers like concise reviews. Avoid verbose... (source)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.56%. Comparing base (6a9e75f) to head (71b3c41).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #166      +/-   ##
==========================================
- Coverage   96.97%   96.56%   -0.42%     
==========================================
  Files          15       13       -2     
  Lines         761      669      -92     
==========================================
- Hits          738      646      -92     
  Misses         23       23              

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