fix(sync): harden sync CLI, IPC, and UI paths from CodeRabbit review

- reject option-like tokens as flag values (--snapshot --force wrote a
  file named --force); --flag=-value still works
- PowerShell remote quoting uses single-quoted literals so $() in a
  quoted path cannot expand
- sync-hosts.json written via temp file + rename; a crash mid-write
  truncated it and the reader's corrupt-fallback dropped every host
- cancelled sync child escalates SIGTERM -> SIGKILL after 5s grace
- NDJSON progress events validated field-by-field before casting
- snapshot filenames include milliseconds to avoid same-second overwrite
- syncAutoScheduler.stop() wired into will-quit cleanup
- sync --ui exclusivity also rejects --make-temp/--remove-temp/--json
- document --sync-window in app help; group --make-temp/--remove-temp
  under modes in sync usage

launcher/config/cli-parser-builder.ts

@@ -351,7 +351,18 @@ export function parseCliPrograms(
       const makeTemp = options.makeTemp === true;
       const removeTemp = typeof options.removeTemp === 'string' ? options.removeTemp.trim() : '';
       if (options.ui === true) {
-        if (host || snapshot || merge || push || pull || check || options.force === true) {
+        if (
+          host ||
+          snapshot ||
+          merge ||
+          push ||
+          pull ||
+          check ||
+          makeTemp ||
+          removeTemp ||
+          options.json === true ||
+          options.force === true
+        ) {
           throw new Error('Sync --ui cannot be combined with other sync options.');
         }
         syncUiTriggered = true;