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**Related issue:** Resolves#38889
Incremental set of slog migration changes for MDM packages.
# Checklist for submitter
- [ ] Changes file added for user-visible changes in `changes/`,
`orbit/changes/` or `ee/fleetd-chrome/changes`.
- already added in a previous PR
## Testing
- [x] Added/updated automated tests
- [x] QA'd all new/changed functionality manually
<!-- This is an auto-generated comment: release notes by coderabbit.ai
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## Summary by CodeRabbit
* **Refactor**
* Standardized logging to Go's structured slog across MDM (Apple,
Windows), DEP/ABM flows, maintained app sync, and related
tests—improving log consistency and contextual diagnostics without
changing user-facing behavior.
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