feat(pipeline): replace QuestionFamilySpec with TaskTypeStrategy

- SlotAssignment: remove family field, strategy looked up at process time
- PipelineConfig: remove family_ratios field
- _assign_slots: remove family_ratios and rng params (pure deterministic)
- _process_one_slot: use get_strategy() for sampling, generation, gates
- Add sub_pattern support (level/constraint override, instruction injection)
- Add strategy.extra_gates() check after standard gates
- load_pipeline_config: stop reading family_ratios from YAML
- Update tools/generate_questions.py seed override and dry-run log
- Update all integration tests to match new API

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

tests/integration/test_cli_generate_v2.py

@@ -45,21 +45,9 @@ class TestCLIGenerateV2:
         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