Fix CI: separate docs deps and add fail-fast: false

The poetry install step failed on Python 3.12 because
pydoc-markdown 2.1.3 (via yapf) is incompatible with 3.12.

- Move mkdocs, pydoc-markdown, mkdocs-material to optional "docs"
  dependency group so they aren't installed during CI test runs
- Add fail-fast: false so one matrix failure doesn't cancel all jobs
- Use --without docs flag in poetry install

https://claude.ai/code/session_017D3uGziwAhF88Zivc51jK5

Author: claude

.github/workflows/tests.yml

@@ -8,6 +8,7 @@ jobs:
     runs-on: ubuntu-latest
 
     strategy:
+      fail-fast: false
       matrix:
         python-version: ["3.9", "3.10", "3.11", "3.12"]
 
@@ -39,7 +40,7 @@ jobs:
           key: venv-${{ runner.os }}-${{ steps.setup-python.outputs.python-version }}-${{ hashFiles('**/poetry.lock') }}
       - name: Install dependencies (if no cache)
         if: steps.cached-poetry-dependencies.outputs.cache-hit != 'true'
-        run: poetry install --no-interaction
+        run: poetry install --no-interaction --without docs
 
       # Linting
       - name: Run flake8

poetry.lock

@@ -25,9 +25,14 @@ pytest = "^7.0"
 flake8 = "^5.0"
 requests-mock = "^1.6"
 pytest-cov = "^4.0"
+black = "*"
+
+[tool.poetry.group.docs]
+optional = true
+
+[tool.poetry.group.docs.dependencies]
 mkdocs = "^1.0"
 pydoc-markdown = "*"
-black = "*"
 mkdocs-material = "^6.1.0"
 
 [build-system]