SteamOS NVIDIA Installer 0.1.3

This maintenance release improves source builds and documents a tested workaround
for the OverlayFS casefold error on SteamOS hosts.

• Enforce LF line endings for patch files and VERSION, including Windows Git
  checkouts and exports with autocrlf enabled.
• Add a regression test for these Linux build inputs.
• Document a file-backed ext4 build workspace without casefold. The existing home
  partition does not need to be reformatted or have its features changed.

The source ZIP generated directly by GitHub for 0.1.2 already had correct line
endings. This correction covers Windows Git conversion.

The recovery base remains SteamOS 3.8.14. The default driver and installed runtime
payload are unchanged from 0.1.2. Existing installations do not need to be rebuilt.

Validation: all four complete-builder components and the installer image built
successfully with the file-backed workspace after LF normalization. The exact
casefold rejection and successful OverlayFS workaround were tested on SteamOS
kernel 6.16.12; the full build ran in an Arch Linux VM. Final source archive checks
passed 180 tests (one skipped) and ShellCheck. This release does not claim a new
hardware installation test.