Adds a simple .sh script that can trigger a refetch locally from a host
if required.
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## Summary by CodeRabbit
* **Documentation**
* Updated the Linux script used to trigger Fleet refetch operations. It
now runs with stricter Bash safety, validates and trims the system
identifier before sending the request, and reports clear success/failure
status while returning the appropriate nonzero exit code on errors.
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Multiple customers have now requested scripts for setting hostnames on
macOS, and a couple for Linux. This adds scripts to the solutions folder
for that purpose.
Linux tested against `Ubuntu 26.04` and `openSUSE Tumbleweed`
macOS tested against `Tahoe 26.4.1`
<!-- This is an auto-generated comment: release notes by coderabbit.ai
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## Summary by CodeRabbit
* **Documentation**
* Added an automated Linux hostname configuration solution that derives
a hostname from the device serial, applies it system-wide, and updates
host entries.
* Added an automated macOS hostname configuration solution that sets
ComputerName/LocalHostName/HostName from the device serial and reports
the new hostname.
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Gray Williams