Add Python and YAML linting to CI pipeline

[Jython1415]

Summary

Implements comprehensive code quality tooling using modern, fast linters to address issue #112.

Changes

Python Linting:

• Added Ruff for linting and formatting (single tool replacing Black + Flake8 + isort)
• Configured in pyproject.toml with:
  • Line length: 100 characters
  • Enabled rulesets: pycodestyle, pyflakes, isort, pep8-naming, pyupgrade, flake8-bugbear, flake8-comprehensions, flake8-simplify, flake8-return
  • Auto-fix enabled for safe violations

YAML Linting:

• Added yamllint for formula YAMLs and workflow files
• Configured in .yamllint with:
  • Line length warnings at 120 characters (accommodates long formulas)
  • 2-space indentation (GitHub Actions standard)
  • Support for truthy values in GH Actions (on/off, yes/no)

CI Integration:

• Updated .github/workflows/test.yml with 3 new steps:
  1. Lint Python code with Ruff
  2. Check Python formatting with Ruff
  3. Lint YAML files with yamllint
• Linting runs before tests to fail fast on style issues

Code Quality Improvements:

• Fixed all existing linting violations:
  • Removed unused imports and variables
  • Fixed import ordering and formatting
  • Simplified nested if statements
  • Added proper exception chaining (raise...from)
  • Applied consistent code formatting
  • Removed trailing whitespace from YAML files

Testing

• ✅ All 156 existing tests pass
• ✅ Formula linter passes (33/33 files)
• ✅ README generation succeeds
• ✅ Ruff linting passes (0 violations)
• ✅ Ruff formatting check passes
• ✅ yamllint passes (0 errors, only warnings for long lines which are acceptable)

Benefits

• Fast: Ruff is 10-100x faster than traditional Python linters
• Simple: Single tool instead of 3-5 separate tools
• Modern: Uses current Python ecosystem standards
• Maintainable: Centralized configuration in pyproject.toml
• Automated: CI fails fast on style violations

Closes #112