feat: Update the project to modern Python and tooling

[dbrattli]

feat!: Modernize OSlash to Python 3.12+ with strict type checking

This PR completes the OSlash modernization plan, bringing the codebase to Python 3.12+ with modern tooling and strict type safety.

🎯 Major Changes

Type System Modernization (Phase 3)

• ✅ PEP 695 type parameters throughout all 22 source files
• ✅ Replaced all TypeVar declarations with modern [T] syntax
• ✅ Added from __future__ import annotations to all modules
• ✅ 0 pyright errors in strict mode (was ~54 errors)
• ✅ Minimized Any usage with justification comments
• ✅ Fixed all type inference issues in core library

Build System & Package Management (Phase 1)

• ✅ Migrated to uv for package management
• ✅ Modern pyproject.toml with PEP 621 metadata
• ✅ Configured release-please for automated versioning
• ✅ Added uv.lock for reproducible builds
• ❌ Removed legacy files: setup.py, setup.cfg, versioneer.py (68k lines!), MANIFEST.in, .flake8, .pylintrc, requirements.txt

Code Quality Tooling (Phase 2)

• ✅ Ruff for linting & formatting (120 char line length)
• ✅ Pyright strict mode with comprehensive rules
• ✅ Pre-commit hooks configured (ruff, pyright, standard checks)
• ✅ Fixed pyright config warning (removed invalid reportAny setting)

Code Improvements

• ✅ Fixed test type annotations - removed all unnecessary # type: ignore comments
• ✅ Added Callable type hints to lambda expressions in tests
• ✅ Removed module-level aliases that lost type information
• ✅ Fixed Observable.just to be proper @classmethod
• ✅ Fixed oslash/do.py with proper type annotations (54 errors → 0)
• ✅ Fixed oslash/list.py head() method with cast
• ✅ Added missing exports (do, guard, let)

CI/CD (Phase 5)

• ✅ Created modern .github/workflows/ci.yml
• ✅ Created .github/workflows/release-please.yml
• ✅ Multi-OS testing (Linux, macOS, Windows)
• ✅ Python 3.12, 3.13, 3.14 support
• ✅ Pre-commit runs in CI

Documentation (Phase 6)

• ✅ Created comprehensive CLAUDE.md development guide
• ✅ Updated README.md with Python 3.12+ requirement and type safety info

📊 Results

• 165 tests passing with 86% code coverage
• 0 pyright errors in main codebase (oslash/)
• 0 warnings from tooling
• Pre-commit hooks working without hanging
• Net change: -68k lines (versioneer removal) + comprehensive type safety

🔧 Breaking Changes

For Users

• ⚠️ Python 3.12+ required (was 3.8+)
• ✅ Public API unchanged (monads work the same way)
• ✅ Better type inference and IDE support

For Contributors

• Must use uv for development
• Pre-commit hooks enforced
• Strict type checking required
• Conventional commits for releases

📝 Files Changed

Deleted (7): setup.py, setup.cfg, versioneer.py, MANIFEST.in, .flake8, .pylintrc, requirements.txt

Created (6): .pre-commit-config.yaml, release-please-config.json, .release-please-manifest.json, .github/workflows/ci.yml, .github/workflows/release-please.yml, CLAUDE.md

Modified (~35): All source files updated with PEP 695 syntax, test files with proper types, configuration files modernized

🎓 Educational Impact

This modernization showcases Python 3.12+ best practices:

• Modern type parameter syntax
• Strict type checking workflows
• Protocol-based design patterns
• Modern Python tooling ecosystem

Perfect for learning functional programming with state-of-the-art Python!

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BREAKING CHANGE: Requires Python 3.12+. This is an educational project showcasing modern Python features. For Python 3.8+ support, use version 0.6.0.