fix: resolve GitHub Actions failures

- Remove Codecov coverage upload causing rate limit errors
- Remove pytest-cov dependency (not needed for CI)
- Simplify test workflow to focus on functionality
- All 37 tests still pass without coverage collection
- Workflow now more reliable and faster

🔧 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

setup.py

@@ -30,7 +30,6 @@ setup(
         "dev": [
             "pytest>=7.4.0",
             "pytest-asyncio>=0.21.0",
-            "pytest-cov>=4.1.0",
             "pytest-mock>=3.11.0",
         ]
     },