Prepare CloudSaveKit 0.2.5

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Summary

• add CloudSaveKit 0.2.5 documentation-only release notes
• update the package installation example to 0.2.5
• restore the changelog introduction to its canonical position

Validation

• AgentGuidelines consumer validation passes at 0.0.32
• Markdown wrapping check passes across README, changelog, and DocC
• static-hosting DocC archive builds without warnings
• git diff check passes

Release

After exact-head review, CI, and merge, publish tag and GitHub release 0.2.5. This release contains no public API or runtime behavior changes.

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ChatGPT exact-head release-blocker review: APPROVED

• Reviewed base: 6098e0f
• Reviewed head: e1dd43b
• P0/P1 findings: None
• Scope verified: CHANGELOG.md and README.md only; documentation-only patch release with no API or runtime changes
• Exact-head CI: Swift Format and Test both pass
• Review conversation: https://chatgpt.com/c/6aa844d6-eac0-83eb-9e71-e52555ea12f7