ci: fail release if gem manifest is out of date

[cb-alish]

The release workflow built the gem directly without regenerating the s.files manifest in chargebee.gemspec. When new files were added but the manifest was not updated, they were silently excluded from the published gem. Add a step that runs make update-manifest and fails the release if chargebee.gemspec differs, preventing missing build artifacts.

Release workflow now regenerates the gem manifest before publishing and fails if chargebee.gemspec is out of date. This ensures the committed s.files list matches the generated manifest, preventing missing files from being omitted from the packaged gem.

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[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Enterprise

Run ID: 122c36c8-cec2-49ef-a073-72db9082d803

📥 Commits

Reviewing files that changed from the base of the PR and between 869476d and 126ea7a.

📒 Files selected for processing (1)

• .github/workflows/release.yml

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Walkthrough

Adds a CI step to the Ruby release workflow that runs make update-manifest and checks chargebee.gemspec for uncommitted diffs, failing the job with diagnostic output if stale, otherwise confirming the manifest is current before gem build/push.

Changes

Release Workflow Manifest Check

Layer / File(s)	Summary
Add gemspec verification step .github/workflows/release.yml	New step runs make update-manifest, diffs chargebee.gemspec, fails with diagnostic diff output on drift, otherwise logs manifest is current.

Estimated code review effort: 1 (Trivial) | ~3 minutes

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