fix: wait for vmware-vmx.exe release before deleteVM

After hard stop, vmware-vmx.exe briefly holds file locks causing
deleteVM to fail with "Insufficient permissions". Replace the fixed
3s sleep with a vmrun-list poll loop (up to 20s) that waits until
the VMX is no longer registered as running, then retry deleteVM up
to 3x with 0/3/6s backoff before falling back to directory removal.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

scripts/Remove-BuildVM.ps1

@@ -72,16 +72,37 @@ $stateOutput = & $VmrunPath -T ws getState $VMPath 2>&1
 if ($stateOutput -match 'running') {
     Write-Host "[Remove-BuildVM] Graceful stop timed out — forcing hard stop..."
     & $VmrunPath -T ws stop $VMPath hard 2>&1 | Out-Null
-    Start-Sleep -Seconds 3
 }
 
-# ── Step 4: Delete VM via vmrun (removes VMX + delta VMDK) ───────────────────
+# Poll vmrun list until VMX is gone — vmware-vmx.exe may hold file locks briefly
+# after stop. Waiting for the entry to disappear ensures deleteVM won't race the
+# process exit.
+$vmxNorm         = $VMPath.Trim().ToLower()
+$releaseDeadline = (Get-Date).AddSeconds(20)
+while ((Get-Date) -lt $releaseDeadline) {
+    $listedVMs = & $VmrunPath -T ws list 2>&1 |
+        Where-Object { $_ -notmatch '^Total running' } |
+        ForEach-Object { "$_".Trim().ToLower() }
+    if ($listedVMs -notcontains $vmxNorm) { break }
+    Start-Sleep -Seconds 2
+}
+
+# ── Step 4: Delete VM via vmrun — retry up to 3× with backoff ────────────────
 Write-Host "[Remove-BuildVM] Deleting VM..."
-$deleteOutput = & $VmrunPath -T ws deleteVM $VMPath 2>&1
-$deleteExit   = $LASTEXITCODE
+$deleteOutput = ''
+$deleteExit   = -1
+foreach ($delay in @(0, 3, 6)) {
+    if ($delay -gt 0) {
+        Write-Host "[Remove-BuildVM] Retrying deleteVM in ${delay}s..."
+        Start-Sleep -Seconds $delay
+    }
+    $deleteOutput = & $VmrunPath -T ws deleteVM $VMPath 2>&1
+    $deleteExit   = $LASTEXITCODE
+    if ($deleteExit -eq 0) { break }
+}
 
 if ($deleteExit -ne 0) {
-    Write-Warning "[Remove-BuildVM] vmrun deleteVM returned exit code $deleteExit : $deleteOutput"
+    Write-Warning "[Remove-BuildVM] vmrun deleteVM failed after retries (exit $deleteExit): $deleteOutput"
     Write-Warning "[Remove-BuildVM] Will attempt manual directory removal."
 }