Show printer idle diagnostics and customer guidance on Windows, macOS and Linux

[sridharkalaibala]

Customers had no visible cross-platform guidance when printers stopped after idle; power diagnostics were hidden in Windows recovery controls. Add an expanded Printer readiness & idle troubleshooting section in Hardware Manager with detected settings, explicit unknown states, KOT sleep-prevention status and OS-specific customer steps.

Windows reuses active-plan Sleep/Hibernate/USB checks and explains desktop Setting versus AC/DC labels. macOS reads pmset sleep policies and CUPS queue/acceptance status. Linux checks CUPS, GNOME idle action/timeouts where available, and read-only USB printer-class power attributes. Linux USB identities are not guessed or assigned to queues; vendor-specific/network devices remain explicitly unverified. Missing tools, permissions and unsupported OS settings produce manual instructions rather than healthy status.

Checks use bounded asynchronous commands, cache system results for one minute and coalesce concurrent requests. They do not print, modify power settings, need elevation, restart spoolers or delete jobs. Windows automatic USB recovery remains Windows-only; this change does not promise universal USB wake or CUPS retry support. Customer instructions are in docs/PRINTER-IDLE-TROUBLESHOOTING.md.

Local verification: full desktop suite on the implementation checkout passed 3,484 tests with four skips; final targeted suite after rebasing onto current develop passed 20 tests. The additional GNOME zero-timeout test passed. Live Windows diagnostics succeeded. macOS/Linux parsing, failures and UI were fixture-tested on Windows; native hardware validation is outstanding. Packaging allowlist and attribution checks passed. No workflows or CI jobs added.

[github-actions]

Merged to develop. Anyone can test this - you do not need write access.

Try it at https://develop.posnic.io, or run it yourself:

git fetch origin develop && git checkout develop
npm install && npm --prefix api install
npm run dev   # then http://localhost:3000

When you have tested it, say what you did and what happened, and set
QA passed or QA failed. If you cannot set labels, just comment -
a maintainer will.

Reporting that something is broken is as useful as fixing it. It is
better found here than by a shopkeeper.