Port TypeScript PR #60303: Fix template string escaping for control characters

[Copilot]

This ports the fix from microsoft/TypeScript#60303 which corrected template string escaping behavior for control characters.

Problem

The template string escaping logic had a subtle bug where the \u001f control character (Unit Separator) was not being escaped when it should have been. The condition ch < '\u001f' was excluding \u001f itself from the escaping logic.

Solution

Changed the condition from ch < '\u001f' to ch <= '\u001f' in the escapeStringWorker function to properly include all control characters up to and including \u001f.

Changes Made

1. Fixed escaping condition in internal/printer/utilities.go:

   // Before
   if ch < '\u001f' || flags&getLiteralTextFlagsNeverAsciiEscape == 0 && ch > '\u007f' {
   
   // After  
   if ch <= '\u001f' || flags&getLiteralTextFlagsNeverAsciiEscape == 0 && ch > '\u007f' {

2. Added comprehensive test cases to verify:

   • LF character (\n) is NOT escaped in template strings (backticks) ✓
   • Other control characters like \u0001, \u001f ARE escaped in template strings ✓
   • Special characters like tab (\t) and vertical tab (\v) are properly escaped ✓

3. Updated test baselines for templateStringControlCharacterEscapes03 tests that now correctly escape control characters.

Verification

The fix was verified by:

• All new unit tests pass
• Existing baseline tests updated to reflect correct behavior
• Build and full test suite passes
• The LF character behavior remains correct (not escaped in template strings)

Fixes #15.

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