Bump pinned Ruby to 3.3.4

[mokagio]

What does it do?

Bumps .ruby-version from 3.2.2 to 3.3.4.

That file feeds .buildkite/shared-pipeline-vars, which derives RUBY_VERSION (the Build & Test matrix) and DOCKER_RUBY_IMAGE (the gem-publish step), so this moves both CI and release builds onto 3.3.4 in one place.

Checklist before requesting a review

• Run bundle exec rubocop — 198 files, no offenses (locally, under 3.3.4).
• Add Unit Tests if applicable — N/A, config-only change.
• Run bundle exec rspec — 893 examples, 0 failures (locally, under 3.3.4); Gemfile.lock unchanged after bundle install.
• CHANGELOG.md entry added under ## Trunk → ### Internal Changes.
• MIGRATION.md — N/A, no breaking change.

How to test

CI itself is the test: this PR's Build & Test step now runs on 3.3.4. Confirm it goes green.

[Copilot]

Pull request overview

This PR updates the repository’s pinned Ruby version to 3.3.4 and records the change in the changelog, which in turn updates the Buildkite CI test matrix and the Docker image used for gem publishing.

Changes:

• Bump .ruby-version from 3.2.2 to 3.3.4.
• Add a CHANGELOG.md entry under Trunk → Internal Changes documenting the Ruby version bump.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
CHANGELOG.md	Documents the Ruby pin bump under Trunk → Internal Changes.
.ruby-version	Updates the pinned Ruby version that feeds CI and release build configuration.

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[mokagio]

Converting to draft — CI surfaced a blocker.

What happened

The Mac queue ran the full suite green on 3.3.4 (🧪 Build and Test, 2m02s), but both linter-cluster jobs failed instantly:

rbenv: version `3.3.4' is not installed (set by .../.ruby-version)
Gem automattic-buildkite-linter is not installed.

• Rubocop — failed (rbenv, before any lint ran)
• Danger – PR Check — failed (same rbenv error; not a label/milestone issue)

Root cause

The shared linter-cluster AMI (buildkite-ci/src/agents/linter/) provisions a fixed rbenv list — currently 3.2.2, 3.2.7, 3.3.7 — with 3.3.7 as the global default. 3.3.4 isn't in that set, so rbenv aborts before the linter gem loads.

Why I'm parking it rather than retargeting

Rather than chase a one-off 3.3.4 (or add 3.3.4 to the linter AMI), this should fold into the existing effort: Support Ruby 3.4 and 4.0. A piecemeal patch bump here would likely be superseded by that work. If we do want an interim bump, 3.3.7 is the version the linter fleet already blesses.

Leaving the branch up for reference.

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Posted by Claude (Opus 4.8) on behalf of @mokagio with approval.