Add Windows support

[kbens]

psa-cli is currently Linux-only. PeopleSoft runs on Windows too — supporting Windows opens psa-cli to Windows-based PeopleSoft administrators.

Current Linux assumptions

• pyproject.toml classifier: Operating System :: POSIX :: Linux
• README + docs claim Linux-only
• CI matrix runs only on ubuntu-latest

Known sticking points

Area	Linux	Windows	Notes
Privilege escalation	sudo	runas / UAC	SudoFileOps would need a Windows backend
File permissions	chmod/chown	NTFS ACLs	Different model entirely
Process invocation	psadmin shell	psadmin.cmd / tmadmin.exe	Path + extension differences
Default paths	/u01/app/...	C:\\PS_*\\...	Need OS-aware defaults
DPK install	DPK for Linux	DPK for Windows (different layout)	Each command needs OS branching
Terminal / ANSI	Native	Windows Terminal OK, cmd.exe limited	Rich handles most of this automatically
Subprocess invocation	Forward slashes, sh-style quoting	Backslashes, cmd-style quoting	subprocess_runner likely needs review

Suggested approach

1. Scope first — survey every subprocess.run, hard-coded /, os.geteuid, sudo, psadmin shell-out, and the prereq-check shell scripts. Identify the actual surface area.
2. Abstract OS-specific behavior behind a small platform layer (e.g. psa.core.platform.escalate(), psa.core.platform.psadmin_cmd()) instead of inlining os.name checks everywhere.
3. Add Windows to the CI matrix (windows-latest). This will quickly surface anything broken.
4. Test against a real Windows PeopleSoft environment for the DPK and domain commands — unit tests won't catch shell-out integration issues.
5. Update README + docs + pyproject classifiers once parity is real.

References

• PeopleSoft DPK for Windows: deployment differs significantly from Linux DPK
• Python pathlib.Path and shutil already handle most cross-platform path work — leverage them