Fix docs CI: install project deps before building with sphinx

uv sync --group docs only installs sphinx, not pytheory's deps
(pytuning, scipy, etc). Autodoc needs to import the package to
generate API reference pages. Now runs uv sync first.

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

.github/workflows/docs.yml

@@ -26,7 +26,7 @@ jobs:
         run: uv python install 3.13
 
       - name: Install dependencies
-        run: uv sync --group docs
+        run: uv sync && uv sync --group docs
 
       - name: Build docs
         run: uv run sphinx-build -b html docs docs/_build/html