Improve speed of sshd tree-sitter grammar

[SteveL-MSFT]

PR Summary

Simplify match to give speed improvement. Before changes:

  invalid_expressions:
      1. ✓ missing space after keyword -- Warning: Slow parse rate (436.364 bytes/ms)
  valid_expressions:
     26. ✓ parse empty line -- Warning: Slow parse rate (370.370 bytes/ms)

After, still have warning on slow parse rate, but significant improvement:

  invalid_expressions:
      1. ✓ missing space after keyword -- Warning: Slow parse rate (679.887 bytes/ms)
  valid_expressions:
     26. ✓ parse empty line -- Warning: Slow parse rate (666.667 bytes/ms)

[Copilot]

Pull request overview

Performance optimization for the sshd tree-sitter grammar by reducing parser ambiguity and inlining hot rules. The _commaSeparatedString rule (which required at least one comma) is merged into a single _stringArg rule that handles both single and comma-separated strings via repeat, eliminating the need for a separate $.string alternative in _argument. Explicit precedence between boolean, number, and string plus inlining _new_line/_argument reportedly improves parse rates by ~60-80%.

Changes:

• Add inline for _new_line and _argument, and a precedences declaration ordering boolean > number > string to resolve token conflicts.
• Replace _commaSeparatedString (requiring repeat1) with _stringArg using repeat, so it now subsumes the bare $.string branch in _argument.
• Flatten a redundant nested seq in the match rule.