fix: normalize literal \n escape sequences in todo list parsing

[roomote-v0]

Related GitHub Issue

Closes: #11977

Description

This PR attempts to address Issue #11977. Some models/providers (e.g. LiteLLM with qwen3-coder-next) send the todos parameter with literal escape sequences -- the two-character string \n (backslash + n) rather than actual newline characters. This causes all checklist items to end up on a single line, so only one todo item gets parsed.

The fix normalizes literal \n and \r\n escape sequences into actual newline characters in parseMarkdownChecklist() before the existing .split(/\r?\n/) call. This is a minimal, targeted change that handles the mismatch without affecting any other behavior.

Files changed:

• src/core/tools/UpdateTodoListTool.ts - Added normalization of literal escape sequences
• src/core/tools/__tests__/updateTodoListTool.spec.ts - Added 3 test cases covering literal \n, literal \r\n, and mixed literal/actual newlines

Test Procedure

• Added unit tests in updateTodoListTool.spec.ts covering:
  • Items separated by literal \n escape sequences
  • Items separated by literal \r\n escape sequences
  • Mixed literal and actual newlines
• All 24 tests pass: cd src && npx vitest run core/tools/__tests__/updateTodoListTool.spec.ts
• Lint and type checks pass across all packages

Pre-Submission Checklist

• Issue Linked: This PR is linked to an approved GitHub Issue (see "Related GitHub Issue" above).
• Scope: My changes are focused on the linked issue (one major feature/fix per PR).
• Self-Review: I have performed a thorough self-review of my code.
• Testing: New and/or updated tests have been added to cover my changes.
• Documentation Impact: No documentation updates are required.
• Contribution Guidelines: I have read and agree to the Contributor Guidelines.

Documentation Updates

• No documentation updates are required.

Additional Notes

Feedback and guidance are welcome.

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