fix: prevent context exhaustion when reading large files

[roomote]

Summary

This PR fixes issue #6069 where the codebase condensing feature fails when Roo Code accidentally tries to read very large source files (>5000 lines), causing the context window to be exhausted.

Changes

• Added file size check (10MB limit) to reject extremely large files before reading
• Added configurable largeFileLineThreshold setting (default: 5000 lines)
• When maxReadFileLine is -1 (no limit) and a file exceeds the threshold, it's automatically truncated to the first 1000 lines
• Added the new configuration to the global settings schema with proper TypeScript types
• Added comprehensive tests for the new functionality

How it works

1. Before reading any file, the tool now checks if it exceeds 10MB and rejects it with a clear error message
2. When maxReadFileLine is set to -1 (unlimited), the tool checks if the file exceeds largeFileLineThreshold
3. If it does, the file is automatically truncated to 1000 lines to prevent context exhaustion
4. This prevents the "Failed to condense" errors and task memory loss reported in the issue

Testing

• Added unit tests for file size rejection
• Added tests for large file threshold behavior
• All existing tests pass

Fixes #6069

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Important

Adds file size and line threshold checks to prevent context exhaustion when reading large files, with new settings and tests.

• Behavior:
  • Adds file size check (10MB limit) in readFileTool.ts to reject large files before reading.
  • Introduces largeFileLineThreshold setting (default: 5000 lines) in global-settings.ts.
  • Truncates files to 1000 lines if maxReadFileLine is -1 and file exceeds threshold.
• Configuration:
  • Adds largeFileLineThreshold to global settings schema in global-settings.ts.
  • Updates webviewMessageHandler.ts to handle largeFileLineThreshold messages.
• Testing:
  • Adds unit tests in readFileTool.spec.ts for file size rejection and line threshold behavior.
  • Ensures all existing tests pass.

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[daniel-lxs]

This is not going to work as 10MB is way more than enough to cause the issue, we should probably perform a quick length check for the file