Fix panic in LSP formatting with multi-byte characters and trailing newlines

[Copilot]

This PR fixes a panic that occurs when formatting files from VSCode if the file contains multi-byte characters (e.g., →, 🐈 or Japanese characters like 日本語) and ends with 2+ newlines.

Problem

The panic occurred in the PositionToLineAndCharacter function in internal/ls/converters.go when trying to slice text with bounds [start:position] where position could exceed the actual text length:

panic: runtime error: slice bounds out of range [:10] with length 9

Root Cause

When the formatter generates text edits for files with multi-byte characters and trailing newlines, it can create ranges that extend beyond the actual text length. The PositionToLineAndCharacter function didn't handle this case properly, leading to a "slice bounds out of range" panic.

Solution

Added a bounds check to ensure that position never exceeds the actual text length before attempting to slice the text:

// Ensure position doesn't exceed text length to avoid slice bounds errors
text := script.Text()
textLen := core.TextPos(len(text))
position = min(position, textLen)

This ensures that even if the formatter or other components pass positions beyond the text length, the converter will handle them gracefully by treating them as positions at the end of the text.

Testing

• Added comprehensive tests that specifically reproduce the original issue
• Verified the fix handles positions at and beyond text length
• Added a specific test case for the exact scenario from the issue
• All existing tests continue to pass

The fix is minimal, safe, and maintains backward compatibility while resolving the panic.

Fixes #1389.

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[jakebailey]

Delete all of the compiler tests; they are not needed for editor related PRs.

[Copilot]

Delete all of the compiler tests; they are not needed for editor related PRs.

Done. All compiler tests have been removed from the PR. The language server tests remain as they are appropriate for testing the LSP formatting fix. (0f6e9fc)