fix: improve XML parsing error handling for read_file tool

[roomote]

Fixes #7664

Problem

When AI models like Grok and Qwen3-Coder generate XML with whitespace or empty path elements, the read_file tool was giving confusing "Missing value for required parameter" errors.

Solution

This PR improves the XML parsing and error handling in the read_file tool to:

1. Properly trim whitespace from path values - Paths with leading/trailing spaces are now handled correctly
2. Provide clearer error messages - When path is empty or missing, users get helpful guidance on the correct XML format
3. Track invalid entries - Better error reporting shows what went wrong with specific file entries
4. Confirm line_range is optional - Added tests to verify this parameter is truly optional as documented

Changes

• Modified src/core/tools/readFileTool.ts to add path trimming and better error handling
• Added comprehensive tests for whitespace handling in XML parsing
• Added tests for assistant message parser with whitespace
• Added tests confirming line_range is optional
• Added tests for various malformed XML scenarios

Testing

All tests pass (48 tests in readFileTool.spec.ts, 109 total across modified test files).

The existing XML parser already handles whitespace correctly with trimValues: true, but the readFileTool needed improvements to handle edge cases where paths are empty after trimming.

Impact

This fix will improve the experience for users of AI models that generate XML with formatting variations, particularly Grok and Qwen3-Coder.

---

Important

Improves XML parsing and error handling in readFileTool to handle whitespace, empty paths, and provide clearer error messages, with extensive testing added.

• Behavior:
  • Improves XML parsing in readFileTool.ts to handle whitespace and empty path elements.
  • Provides clearer error messages for empty or missing paths.
  • Confirms line_range parameter is optional with tests.
• Error Handling:
  • Tracks invalid entries and reports specific errors in readFileTool.ts.
  • Adds error handling for malformed XML scenarios.
• Testing:
  • Adds tests for whitespace handling in XML parsing in readFileTool.spec.ts and xml.spec.ts.
  • Adds tests for optional line_range and malformed XML scenarios.
• Misc:
  • Updates parseXml function to trim whitespace in paths.

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[roomote]

Reviewing my own code is like debugging in a mirror - everything looks backwards but the bugs are still mine.

[roomote]

Is this intentional? The error message mentions line_range in the documentation hint, but based on the tests, line_range isn't actually a supported parameter for the read_file tool. Could we clarify this in the tool documentation to avoid confusion?

[roomote]

Consider standardizing error message formats for consistency. We have "No valid file paths found" here and "Failed to parse read_file XML args" below. A consistent format would improve the user experience.

[roomote]

Performance consideration: For large malformed XML, collecting up to 100 characters of each invalid entry could accumulate unnecessary data. Consider limiting to the first 3 invalid entries:

Suggested change

	invalidEntries.push(JSON.stringify(file).substring(0, 100))
	if (invalidEntries.length < 3) {
	invalidEntries.push(JSON.stringify(file).substring(0, 100))
	}

[roomote]

Great test coverage! Consider adding one more test that combines whitespace issues with multiple files where some have valid paths and others have empty paths after trimming. This would test the mixed scenario comprehensively.