feat: add concurrent runner for batch CLI execution

Add a Python-based concurrent runner that executes multiple Qwen CLI tasks
across different models in parallel using isolated git worktrees.

Features:
- Execute N tasks × M models concurrently with configurable concurrency
- Create isolated git worktrees for each run under ~/.qwen/worktrees
- Real-time progress display with Rich library
- Capture stdout, stderr, and OpenAI API logs per run
- Atomic JSON tracking of all runs with status and metadata
- Automatic cleanup of worktrees after each run

Structure:
- runner.py: Main implementation with asyncio
- requirements.txt: Python dependencies
- README.md: Documentation and usage
- config.example.json: Configuration template
- examples/: Toy example with sample config and project

Usage:
  python runner.py config.json

Each run creates an isolated output directory:
  outputs/{run_id}/
    ├── stdout.txt
    ├── stderr.txt
    └── logs/openai-*.json

Co-authored-by: Qwen-Coder <qwen-coder@alibabacloud.com>

integration-tests/concurrent-runner/examples/toy-config.json

@@ -0,0 +1,26 @@
+{
+  "concurrency": 2,
+  "yolo": true,
+  "source_repo": "/Users/andy/workspace/projects/qwen-code/integration-tests/concurrent-runner/examples/toy-project",
+  "worktree_base": "~/.qwen/worktrees",
+  "outputs_dir": "./examples/outputs",
+  "results_file": "./examples/results.json",
+  "tasks": [
+    {
+      "id": "task-1",
+      "name": "Rabbit Counting",
+      "prompts": [
+        "Suppose we have 3 rabbits and 4 carrots. How many animals are there?"
+      ]
+    },
+    {
+      "id": "task-2",
+      "name": "AGI Prediction",
+      "prompts": [
+        "Use shell tool to get current date",
+        "Predict how many dates left until we have AGI (artificial general intelligence)"
+      ]
+    }
+  ],
+  "models": ["qwen3-coder-plus", "kimi-k2.5"]
+}