feat: add UserMessage widget and UI backend selection during onboarding

- Introduced UserMessage widget for displaying user input with a styled prompt.
- Updated onboarding steps to include UI backend selection (Rich CLI or Textual TUI).
- Modified EvoScientistConfig to store selected UI backend.
- Enhanced configuration handling to support UI backend environment variable.
- Updated README with new UI backend options and commands.
- Added tests for new UI backend functionality and UserMessage widget.
- Removed obsolete test files and ensured existing tests are updated accordingly.

.github/workflows/lint.yml

@@ -13,7 +13,8 @@ jobs:
       - uses: actions/setup-python@v5
         with:
           python-version: "3.11"
-      - name: Install ruff
-        run: pip install ruff
+          cache: pip
+      - name: Install dependencies
+        run: pip install -e ".[dev]"
       - name: Run ruff
         run: ruff check .