feat(sync): Windows machines work as sync remotes

Remote temp dirs are now created and removed by the remote SubMiner
itself (sync --make-temp / --remove-temp, validated against its own
tmpdir) instead of mktemp/rm, and the flow detects the remote shell
(POSIX, cmd, PowerShell) to pick quoting and SubMiner install-location
candidates - %LOCALAPPDATA% app install, launcher shim, or PATH - with
no POSIX PATH prefix on Windows. Remote temp paths are normalized to
forward slashes for scp and the CLI. Verified end-to-end against a
throwaway sshd with the app binary as the resolved remote command.

launcher/types.ts

@@ -123,6 +123,8 @@ export interface Args {
   syncForce: boolean;
   syncJson: boolean;
   syncCheck: boolean;
+  syncMakeTemp: boolean;
+  syncRemoveTempPath: string;
   syncUi: boolean;
   logLevel: LogLevel;
   logRotation: LogRotation;