feat: add non-propagate option for memory patch

[evan-ak]

📝 Pull Request Summary

Please provide a short summary explaining the purpose of this PR.

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✅ What does this PR do?

• Adds a propagate: bool = True parameter to create_memory_item, update_memory_item, and delete_memory_item in both PatchMixin and CRUDMixin.
• When propagate=False, the memory item is created/updated/deleted as usual, but category summary re-generation is skipped.

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🤔 Why is this change needed?

• In some workflows (e.g. bulk imports or migrations), patching category summaries on every individual memory write is unnecessary and expensive. This option lets callers opt out of propagation when they know category summaries will be rebuilt separately or don't need updating.

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🔍 Type of Change

Please check what applies:

• Bug fix
• New feature
• Documentation update
• Refactor / cleanup
• Other (please explain)

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✅ PR Quality Checklist

• PR title follows the conventional format (feat:, fix:, docs:)
• Changes are limited in scope and easy to review
• Documentation updated where applicable
• No breaking changes (or clearly documented)
• Related issues or discussions linked

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📌 Optional

• Screenshots or examples added (if applicable)
• Edge cases considered
• Follow-up tasks mentioned