release: bump all packages to 0.1.1, add PyPI metadata and CHANGELOG

- Add readme field to all three pyproject.toml files (populates PyPI description page)
- Bump versions to 0.1.1 and update behave-core pin in shell/text
- Update Install sections in root, BEHAVE-SHELL, and BEHAVE-TEXT READMEs to lead with pip install from PyPI
- Add CHANGELOG.md at project root (Keep-a-Changelog format)

BEHAVE-SHELL/README.md

@@ -14,8 +14,12 @@ aggregates, and cryptographic hashes — never raw keystrokes or command text.
 ## Install
 
 ```bash
-pip install -e ../core/ -e .
-# development (pytest + ruff):
+pip install behave-shell
+```
+
+For local development (pytest + ruff):
+
+```bash
 pip install -e ../core/ -e ".[dev]"
 ```