fix(test): restore pruned live boot entries and verify mounted ESP

dev/iso-smoke.py

@@ -651,8 +651,9 @@ def qemu_argv(qemu, scratch, disk, code, variables, iso, memory, *, keep_cdrom_d
         if not Path(iso).is_file():
             raise SmokeError('Trusted ISO must exist as a regular file')
     if keep_cdrom_drive:
-        # Keep one SATA0 device even without media so OVMF retains its DVD boot
-        # entry across ISO-free boots. No file= means there is no optical medium.
+        # Keep SATA0 stable so a saved DVD boot option has the same device path
+        # when media returns. OVMF may still prune the empty drive's boot entry.
+        # No file= means there is no optical medium.
         optical = 'if=ide,index=0,id=acceptance-cdrom,media=cdrom,readonly=on'
         if iso is not None:
             optical += ',format=raw,file=' + qemu_path(iso)