Improve expression parser with double quote support and comprehensive test suite

[Copilot]

• Analyze existing expression parser implementation
• Run existing test suites to understand current state
• Verify parser already supports parentheses, || and && operators
• Fix double quote handling in tokenizer (was only handling single quotes)
• Add comprehensive test suite with 200+ test cases covering:
  • Complex operator precedence scenarios
  • Nested parentheses expressions
  • Error handling for malformed expressions
  • String literals with special characters
  • Whitespace handling edge cases
  • Real-world GitHub Actions expressions
  • Integration with expression safety validation
  • Mixed quote type handling (single quotes inside double quotes, etc.)
• Add performance benchmarks showing ~675ns per operation
• Address code review feedback about quote handling
• Fix formatting and lint issues (trailing whitespace, missing newline)
• Validate all changes with existing test suite (all tests pass)

Original prompt

Improve expression parser (the parser that validates that expressions are safe to use) to support:

• parenthesis
• || operator
• && operator

Add extensive test suite.

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[pelikhan]

@copilot format and fix lint issues

[Copilot]

@copilot format and fix lint issues

Fixed formatting and lint issues. Ran go fmt to clean up trailing whitespace and added missing newline at end of file. All linting and tests pass. Commit: 5c90e35