Clean up sloppy lexer code and test dependencies from initial implementation

[Copilot]

This PR addresses the "code slop from first initial pass" by cleaning up repetitive patterns, removing dead code, and fixing test dependencies in the lexer implementation.

Changes Made

Lexer Improvements

• Consolidated repetitive patterns: Replaced 8 nearly identical scoped variable handling blocks with a single helper method try_match_scoped_variable()
• Extracted magic numbers to constants:
  • SILENT_BANG_LENGTH = 7
  • ELLIPSIS_LENGTH = 3
  • FUNCTION_KEYWORD_LENGTH = 8
• Added reusable helper methods:
  • add_token(type, value) - standardizes token creation
  • advance_position(length) - handles position tracking
• Removed dead code: Eliminated commented-out string regex pattern
• Removed redundant keyword matching: The TOKEN_TYPES hash had a keyword regex that conflicted with explicit keyword handling

Test Cleanup

• Fixed dependency issues: Removed unnecessary pry requirement that was causing test failures
• Removed unused code: Eliminated the complex print_ast method in spec_helper that had style violations and wasn't being used
• Fixed unused variable warning in parser_spec.rb

Code Quality

• Applied RuboCop auto-corrections for consistent style
• Added frozen string literal comments and proper formatting
• Improved code organization and readability

Before/After Comparison

Before:

• 8 repetitive scoped variable blocks (v:, s:, b:, w:, t:, g:, l:, a:)
• Magic numbers scattered throughout (7, 3, 8)
• Commented dead code
• Test dependency issues preventing clean runs

After:

• Single configurable helper method with pattern mapping
• Named constants for all magic numbers
• Clean, focused code with no dead weight
• All tests passing cleanly

Impact

• Net reduction: 60 lines of code removed while maintaining full functionality
• Maintainability: Easier to add new scoped variable types
• Reliability: All lexer and unit tests continue to pass
• Style: Consistent formatting and Ruby best practices

The lexer functionality remains exactly the same - this is purely a cleanup refactor that makes the code more maintainable and removes the "late night session" technical debt.

Fixes #1.

Warning

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