- Version bump from 4.2.1 to 4.2.2
- Updated changelog with FlatStore improvements

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-authored-by: Claude <noreply@anthropic.com>

* Define dynamic accessors without evaluating source strings

Parsing an article, collection or section whose translated_content had a
locale key such as "pt-BR" or "zh-CN" raised a SyntaxError, because the key
was interpolated into a string passed to instance_eval and is not a valid
method name. The error is not a StandardError so callers could not rescue it.

Define the accessors with define_method and instance_variable_get/set
instead, normalising the instance variable name. Behaviour for ordinary
keys is unchanged.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

* Keep original attribute keys in serialised output

Hyphenated keys such as pt-BR were emitted as pt_BR by to_hash,
to_json and to_submittable_hash.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

* Upgrade CircleCI config to version 2.1

CircleCI no longer accepts version 2 configs, so pipelines on this
repo error before any job runs and the required test checks never
report.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

* Keep CI check names while using 2.1-compatible job keys

Version 2.1 rejects dots in job keys. Setting the original names on the
workflow jobs keeps the reported check names unchanged.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

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Co-authored-by: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

Co-authored-by: Claude Opus 5.5 (1M context) <noreply@anthropic.com>