Remove poethepoet, use direct commands in CI

Replace all poe task runner usage with direct pytest/sphinx/ruff
commands. Remove poethepoet dependency and [tool.poe.tasks] config.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docs/source/sandbox.md

@@ -12,24 +12,25 @@ uv venv
 ```
 
 Install project in editable mode, including
-all runtime extensions and development tools.
+all development tools.
 ```shell
 uv pip install --upgrade --editable '.[develop,docs,release,test]'
 ```
 
 ## Operations
-Invoke linter and software tests.
+Run tests.
 ```shell
 source .venv/bin/activate
-poe check
+pytest
 ```
 
 Format code.
 ```shell
-poe format
+ruff format .
+ruff check --fix .
 ```
 
 Documentation authoring.
 ```shell
-poe docs-autobuild
+sphinx-autobuild --open-browser --watch docs/source docs/source docs/build
 ```