AHCI storage for laptop images, plaintext password fix

Laptop images now use AHCI storage + e1000 network instead of VirtIO.
This fixes "inaccessible boot device" on real hardware — the AHCI→NVMe
driver transition is handled by Windows, unlike VirtIO→NVMe which isn't.

- makeImage: useAHCI flag switches disk to ide-hd and network to e1000
- customizeImage: auto-detects useAHCI from original image, propagates it
- win10/win11 laptop images: useAHCI = true
- vmix run: --ahci flag for running laptop images in QEMU
- generalize: PlainText password tags in OOBE unattend XML

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

lib/images/windows/templates/generalize.nix

@@ -127,6 +127,7 @@ in
               <LocalAccount wcm:action="add">
                 <Password>
                   <Value>${password}</Value>
+                  <PlainText>true</PlainText>
                 </Password>
                 <Group>Administrators</Group>
                 <Name>${username}</Name>
@@ -136,6 +137,7 @@ in
           <AutoLogon>
             <Password>
               <Value>${password}</Value>
+              <PlainText>true</PlainText>
             </Password>
             <Enabled>true</Enabled>
             <Username>${username}</Username>