Refine Windows installer shutdown process for improved reliability

- Updated the `restartFarmControlAfterUpdate` function to terminate the Farm Control process directly, avoiding potential issues with tree kills that could affect the installer itself.
- Added a PowerShell command to clean up any lingering CEF helper processes after the main process exits, ensuring a smoother update experience without blocking file renames.

packaging/windows/installer.nsh

@@ -345,12 +345,15 @@ Function restartFarmControlAfterUpdate
     ; builds can keep bun/renderer processes alive after the launcher exits.
     System::Call 'kernel32::OpenProcess(i 0x00100000, i 0, i $UpdateParentPid) p .r0'
     ${If} $0 != 0
-      ; Allow two seconds for a graceful exit, then terminate the process tree.
+      ; Allow two seconds for a graceful exit, then terminate the process.
       System::Call 'kernel32::WaitForSingleObject(p r0, i 2000) i .r1'
       ${If} $1 == 258
         !insertmacro progressStatus "Stopping Farm Control..."
-        DetailPrint "Farm Control process $UpdateParentPid did not exit; terminating its process tree..."
-        ExecWait 'taskkill /F /T /PID $UpdateParentPid' $R0
+        DetailPrint "Farm Control process $UpdateParentPid did not exit; terminating it..."
+        ; Never use taskkill /T here: this installer is a direct child of the
+        ; updater process, so a tree kill would terminate the installer itself
+        ; before the folder swap (CEF builds hung at "Stopping Farm Control...").
+        ExecWait 'taskkill /F /PID $UpdateParentPid' $R0
 
         ; Verify that taskkill actually terminated the process before swapping.
         System::Call 'kernel32::WaitForSingleObject(p r0, i 10000) i .r1'
@@ -389,6 +392,13 @@ Function restartFarmControlAfterUpdate
   ${EndIf}
 
   restart_wait_done:
+    ; CEF helper processes normally exit on their own once the main process is
+    ; gone, but sweep up any stragglers still running from the install
+    ; directory so the rename cannot be blocked. Matching on executable path
+    ; (not a tree kill) guarantees this installer, which runs from the Updates
+    ; folder, is never terminated.
+    ExecWait `powershell.exe -NoLogo -NoProfile -NonInteractive -ExecutionPolicy Bypass -Command "Get-CimInstance Win32_Process | Where-Object { $$_.ExecutablePath -like '$FinalInstDir\*' } | ForEach-Object { Stop-Process -Id $$_.ProcessId -Force -ErrorAction SilentlyContinue }"` $R0
+
     ; Give CEF descendants a moment to release DLLs before renaming the tree.
     Sleep 3000