feat(question_gen): add generate-v2 CLI subcommand and experiment script

- Add generate-v2 subparser with --config, --store-dir, --db-path,
  --seed, and --dry-run arguments to tools/generate_questions.py
- Implement _run_generate_v2 async handler: config loading, video
  discovery, DI client construction, TreeIndex loading, pipeline
  invocation, and result persistence
- Add scripts/generate_questions_v2.sh following build_trees.sh
  conventions (source .env, conda run python path, MODE=mock support)
- Update app/question_gen/__init__.py to export full v2 public API:
  run_pipeline_v2, PipelineConfig, PipelineResult, QuestionFamilySpec,
  ALL_FAMILIES, CandidateQuestion, generate_one_v2, GateReport, run_gates
- Add QuestionGenStore.load_progress() for pipeline resumption
- Add integration tests for CLI help and dry-run behavior
- Update test_question_gen_api to match expanded __all__

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

tests/integration/test_cli_generate_v2.py

@@ -0,0 +1,102 @@
+"""generate-v2 CLI 子命令集成测试 — 验证 CLI 入口、dry-run 模式与参数解析。
+
+测试策略：
+- test_subcommand_help: 验证子命令注册成功、--help 返回码 0 且包含 --config
+- test_dry_run: 验证 dry-run 模式不调用 LLM/VLM，仅输出统计信息
+"""
+
+from __future__ import annotations
+
+import subprocess
+import sys
+from pathlib import Path
+
+PROJECT_ROOT = Path(__file__).resolve().parent.parent.parent
+
+
+class TestCLIGenerateV2:
+    """generate-v2 子命令 CLI 集成测试。"""
+
+    def test_subcommand_help(self) -> None:
+        """验证 generate-v2 子命令已注册，--help 正确退出并包含 --config 参数说明。"""
+        result = subprocess.run(
+            [
+                sys.executable,
+                str(PROJECT_ROOT / "tools" / "generate_questions.py"),
+                "generate-v2",
+                "--help",
+            ],
+            capture_output=True,
+            text=True,
+            timeout=30,
+        )
+        assert result.returncode == 0, f"stderr: {result.stderr}"
+        assert "--config" in result.stdout
+        assert "--store-dir" in result.stdout
+        assert "--dry-run" in result.stdout
+
+    def test_dry_run(self, tmp_path: Path) -> None:
+        """验证 dry-run 模式：加载配置、计算 slot，但不调用 LLM/VLM。
+
+        通过创建最小 config + 临时 store-dir 来验证 dry-run 的快速退出行为。
+        """
+        # 创建最小配置文件
+        config_path = tmp_path / "config.yaml"
+        config_path.write_text(
+            """\
+question_gen_v2:
+  family_ratios:
+    retrieval: 0.30
+    reasoning: 0.25
+    enumeration: 0.20
+    visual: 0.15
+    spatial: 0.10
+  gate:
+    blind_answer_model: "mock"
+    leak_test_model: "mock"
+    key_verify_model: "mock"
+    multi_true_model: "mock"
+  dedup_threshold: 0.85
+  retry_limit: 3
+  heavy_sample_rate: 0.15
+  heavy_agent_model: "mock"
+  output_dir: "{output_dir}"
+  per_type: 2
+  concurrency: 2
+  seed: 42
+""".format(output_dir=str(tmp_path / "output")),
+            encoding="utf-8",
+        )
+
+        # 创建 store-dir 结构：至少一个带 tree.json 的视频目录
+        store_dir = tmp_path / "store"
+        videos_dir = store_dir / "videos"
+        video_dir = videos_dir / "test_video_001"
+        video_dir.mkdir(parents=True)
+        # 最小 tree.json（仅需存在）
+        (video_dir / "tree.json").write_text("{}", encoding="utf-8")
+
+        db_path = tmp_path / "question_gen.db"
+
+        result = subprocess.run(
+            [
+                sys.executable,
+                str(PROJECT_ROOT / "tools" / "generate_questions.py"),
+                "generate-v2",
+                "--config",
+                str(config_path),
+                "--store-dir",
+                str(store_dir),
+                "--db-path",
+                str(db_path),
+                "--dry-run",
+            ],
+            capture_output=True,
+            text=True,
+            timeout=30,
+        )
+        assert result.returncode == 0, f"stderr: {result.stderr}"
+        # dry-run 应输出 slot 统计信息到 stderr（loguru 输出）
+        assert "dry-run" in result.stderr.lower() or "slot" in result.stderr.lower()
+        # 确保没有创建 telemetry db（意味着未初始化 LLM 客户端）
+        # DB 可能会被创建用于 store，但不应有 telemetry 调用

tests/unit/test_question_gen_api.py

@@ -35,13 +35,24 @@ class TestQuestionGenPublicAPI:
         assert hasattr(mod, "stratified_sample")
 
     def test_all_exports(self) -> None:
-        """__all__ 包含预期的公开 API（loader + synthesizer）。"""
+        """__all__ 包含预期的公开 API（v1 + v2）。"""
         mod = importlib.import_module("app.question_gen")
         assert set(mod.__all__) == {
+            # v1 接口
             "load_benchmark",
             "stratified_sample",
             "TASK_TYPE_LEVEL_MAP",
             "AnchorContext",
             "generate_one",
             "sample_anchor",
+            # v2 接口
+            "run_pipeline_v2",
+            "PipelineConfig",
+            "PipelineResult",
+            "QuestionFamilySpec",
+            "ALL_FAMILIES",
+            "CandidateQuestion",
+            "generate_one_v2",
+            "GateReport",
+            "run_gates",
         }