Fix import recovery checkpoints and retries

[DeusExTaco]

Summary

• make deferred import recovery checkpoints durable and restart-safe
• process source rechecks in bounded pages without holding database locks across archive inspection
• harden diagnostic database snapshots when user-linked records exist
• document the updated recovery and performance behavior

Validation

• not rerun for the final commit, per request
• pull request CI is the release gate

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-14T22:47:53.890661Z	8d599b7	PR opened

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[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: 8d599b72f3

ℹ️ About Codex in GitHub

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• Comment "@codex review".

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