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.

src/main/sync-cli.ts

@@ -17,6 +17,7 @@ import {
 import { formatMergeSummary, mergeSnapshotIntoDb } from '../core/services/stats-sync/merge';
 import {
   assertSafeSshHost,
+  detectRemoteShellFlavor,
   resolveRemoteSubminerCommand,
   runScp,
   runSsh,
@@ -122,6 +123,7 @@ function buildSyncCliDeps(): SyncFlowDeps {
     formatMergeSummary,
     findLiveStatsDaemonPid,
     assertSafeSshHost,
+    detectRemoteShellFlavor,
     resolveRemoteSubminerCommand,
     runScp,
     runSsh,