HLSL: bump to shader-language-server v1.3.1, remove CRLF workaround

The upstream fix for the CRLF stale-tree crash (antaalt/shader-sense#44)
was merged and released as v1.3.1. This commit:

- Removes the client-side CRLF workaround (open_file override and
  _preload_crlf_content helper) added in #1305, along with the
  now-unused imports.
- Bumps _DEFAULT_VERSION to 1.3.1 and updates SHA-256 checksums for
  all three pre-built platform archives (win-x64, linux-x64, win-arm64).

The regression test (test_include_file_document_symbols_directly) that
exercises the original crash scenario passes against v1.3.1 without the
workaround.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docs/02-usage/050_configuration.md

@@ -472,7 +472,7 @@ Supported settings:
 | Setting | Default | Description |
 |---|---|---|
 | `ls_path` | managed install or build | Override the `shader-language-server` executable path. |
-| `version` | `1.3.0` | Override the bundled version Serena downloads, or builds from source on macOS, when `ls_path` is not set. |
+| `version` | `1.3.1` | Override the bundled version Serena downloads, or builds from source on macOS, when `ls_path` is not set. |
 
 
 #### Haxe