fix: normalize CRLF line endings in prompt file parser

[majiayu000]

Description

Fixes #11876

parsePromptFile() splits on "\n---\n" to separate frontmatter from the prompt body. When the file has CRLF line endings (common on Windows), this split fails because the separator is actually "\r\n---\r\n". The frontmatter doesn't get parsed, so the slash command name and description fall back to the filename instead of the values in the YAML block.

Fixed by normalizing \r\n to \n at the top of parsePromptFile() before any splitting happens. This is the same pattern already used in packages/config-yaml/src/markdown/markdownToRule.ts.

Checklist

• I've read the contributing guide
• The relevant docs, if any, have been updated or created
• The relevant tests, if any, have been updated or created

Tests

Added core/promptFiles/parsePromptFile.test.ts with 7 test cases:

• LF content (baseline)
• CRLF content (the bug)
• Mixed line endings
• No frontmatter fallback
• <system> tag with CRLF
• Default version
• Explicit version in frontmatter

All pass with NODE_OPTIONS=--experimental-vm-modules npx jest promptFiles/parsePromptFile.test.ts.

---

Summary by cubic

Normalize CRLF line endings in the prompt file parser so frontmatter parses on Windows. This makes the command name, description, and system message come from YAML instead of the filename.

• Bug Fixes
  • Normalize \r\n to \n at the start of parsePromptFile() before splitting on \n---\n.
  • Add Vitest tests for LF/CRLF, no-frontmatter fallback, and <system> parsing.
  • Remove a duplicate .test.ts file to fix Prettier CI failure.

^{Written for commit 89482b4. Summary will update on new commits.}

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[cubic-dev-ai]

No issues found across 2 files

[majiayu000]

I have read the CLA Document and I hereby sign the CLA