Add changelog entry and development guidelines

- Add changelog_entry.yaml for taxcalc removal
- Create CLAUDE.md with development guidelines for future work
- Ensure files end with newlines to pass lint checks

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

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

Author: MaxGhenis

CLAUDE.md

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+# Claude Development Guidelines for microdf
+
+## Code Style
+- All files must end with a newline character
+- Run `make lint` before committing to catch style issues
+
+## Changelog Requirements
+- Every PR must include a `changelog_entry.yaml` file at the root
+- Format:
+  ```yaml
+  - bump: patch|minor|major
+    changes:
+      added|changed|removed|fixed:
+      - Description of change
+  ```
+- The file must not be empty and must end with a newline
+
+## Testing
+- Run tests with: `python3 -m pytest microdf/tests/ -v`
+- Ensure all tests pass before creating a PR
+
+## Pull Request Process
+1. Create a feature branch from master
+2. Make changes and ensure they follow code style guidelines
+3. Add a changelog entry
+4. Create PR with descriptive title and body
+5. PRs should close related issues using "Closes #XXX" in the body
+
+## Dependencies
+- Dependencies are managed in `pyproject.toml`
+- Optional dependencies go in `[project.optional-dependencies]`
+- When removing dependencies, also remove from `microdf/_optional.py` VERSIONS dict
+
+## Documentation
+- Documentation notebooks are in `docs/` directory
+- When removing functionality, consider impact on documentation examples

changelog_entry.yaml

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+- bump: minor
+  changes:
+    removed:
+    - Remove all taxcalc functionality and dependencies from the package.
+    - Delete taxcalc.py module and associated test file.
+    - Remove taxcalc from optional dependencies in pyproject.toml.