refactor: stateful Solver instances and two-step solve API

.github/workflows/test.yml

@@ -82,7 +82,7 @@ jobs:
     - name: Install package and dependencies
       run: |
         python -m pip install uv
-        uv pip install --system "$(ls dist/*.whl)[dev,solvers]"
+        uv pip install --system "$(ls dist/*.whl)[dev,solvers,oetc]"
 
     - name: Test with pytest
       env:

CLAUDE.md

@@ -4,6 +4,13 @@ This file provides guidance to Claude Code (claude.ai/code) when working with co
 
 ## Common Development Commands
 
+Before running any commands, ensure you have activated the virtual environment:
+
+```bash
+uv sync --extra dev --extra solvers --extra oetc
+source .venv/bin/activate
+```
+
 ### Running Tests
 ```bash
 # Run all tests (excluding GPU tests by default)
@@ -43,15 +50,6 @@ mypy .
 pre-commit run --all-files
 ```
 
-### Development Setup
-```bash
-# Create virtual environment and install development dependencies
-python -m venv venv
-source venv/bin/activate  # On Windows: venv\Scripts\activate
-pip install uv
-uv pip install -e .[dev,solvers]
-```
-
 ## High-Level Architecture
 
 linopy is a linear optimization library built on top of xarray, providing N-dimensional labeled arrays for variables and constraints. The architecture follows these key principles: