Description
## Context
Follow-up to #9 (closed). On 2026-04-22 we confirmed the root cause: bodies where hydrabody directly launches `sunshine.exe` (without registering the `SunshineService` Windows service) show the Sunshine console/terminal window on top of the kiosk. Bodies where `SunshineService` is registered (spawned by `C:\Sunshine\tools\sunshinesvc.exe`, parent `services.exe`, running as LocalSystem) do not show a console.
Evidence:
- wobbly (airborne-two): no `SunshineService` registered → hydrabody direct-launches sunshine.exe → console visible. Manually ran `New-Service` today to register it; console disappeared.
- cosmic (tvl-body-one): `SunshineService` already registered → no console visible. Someone had run `install-service.bat` on that machine at some point.
- Both machines have the complete `C:\Sunshine\` tree including `tools\sunshinesvc.exe` (the service wrapper binary) and `scripts\install-service.bat` (the registration script). So the tooling is present; registration is just missing.
## Proposal
Update `hydrabody/pkg/provider/provision_windows.go` so that after `installProvider()` extracts the Sunshine distribution, it also:
1. Runs `C:\Sunshine\scripts\install-service.bat` (or equivalently calls `New-Service` / `sc create`) to register `SunshineService` with `binPath=C:\Sunshine\tools\sunshinesvc.exe`, `start=auto`, `obj=LocalSystem`.
2. Runs `C:\Sunshine\scripts\autostart-service.bat` (sets auto-start).
3. Starts the service.
4. Skips the direct-launch code path (`startProvider` should check for the service first and only fall back to direct-launch if the service is not registered — or remove direct-launch entirely).
## Rollout
- Idempotent: if `SunshineService` already exists, skip registration but verify `start=auto`.
- Tag a hydrabody patch release via normal CI.
- On bodies that currently direct-launch, the next hydrabody update will register the service and switch over (with a brief provider-restart window).
## Why this matters
Fleet-wide cosmetic fix (no Sunshine console ever visible to kiosk viewers). Also: the service approach is what Sunshine's own installer does, so we stop diverging from upstream defaults.
## References
- #9 "Sunshine terminal window visible on top when WebRTC stream starts" (closed, but structural fix was never landed)
- Manual fix applied on wobbly on 2026-04-22 as a short-term workaround