Drop .install from the Windows install disk image name

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

run-windows11.py

@@ -153,7 +153,7 @@ Options:
   --install-from-iso  Install from ISO when the system disk is missing
   --install-from-img  Like --install-from-iso, but install from the disk image
                       made by vm-images/build-windows-install-disk.sh, which
-                      is the ISO path ending in .install.img instead of .iso.
+                      is the ISO path ending in .img instead of .iso.
                       It is attached as an NVMe disk, much faster than the
                       emulated USB CD-ROM, and is never modified
   --state-dir DIR     Directory for the VM disk, seed ISO and runtime files
@@ -167,7 +167,7 @@ Options:
 Environment variables:
   WIN11_VM_BASE_IMAGE   Windows 11 base QCOW2 image (default: beside shared images)
   WIN11_VM_INSTALL_ISO  Windows 11 installation ISO used with --install-from-iso
-                        (--install-from-img uses the same path ending in .install.img)
+                        (--install-from-img uses the same path ending in .img)
   WIN11_VM_TOOLS_ISO    VirtIO Windows tools ISO (default: resolved by shared image helper)
   WIN11_VM_RDP_PORT     Host RDP port (default: 3389)
   WIN11_VM_SSH_PORT     Host SSH port (default: 2222)
@@ -262,7 +262,7 @@ if not disk_image.is_file():
             env("WIN11_VM_INSTALL_ISO")
             or capture([str(image_downloader), "--print-path", "windows11", "--iso"]))
         if install_from_img:
-            install_iso = install_iso.with_suffix(".install.img")
+            install_iso = install_iso.with_suffix(".img")
         uses_shared_tools_iso = False
         if env("WIN11_VM_TOOLS_ISO"):
             tools_iso = Path(env("WIN11_VM_TOOLS_ISO"))