refactor: Organize generator tests into dedicated folders

Move InsightfulTextGenerator tests into nested folder structure:
- Created: tests/agentune/analyze/feature/gen/insightful_text_generator/
- Moved 7 test files: test_e2e.py, test_e2e_blackbox.py, test_feature_classes.py,
  test_llm_based_deduplicator.py, test_prompts.py, test_type_detection.py, test_utils.py
- Added __init__.py to new folder
- Updated conftest.py import paths

This matches the SemanticInsightsGenerator test structure and provides
better organization as more generators are added.

Test structure now:
tests/agentune/analyze/feature/gen/
├── insightful_text_generator/  # TextInsights tests
│   ├── __init__.py
│   ├── test_e2e.py
│   ├── test_e2e_blackbox.py
│   ├── test_feature_classes.py
│   ├── test_llm_based_deduplicator.py
│   ├── test_prompts.py
│   ├── test_type_detection.py
│   └── test_utils.py
├── semantic_insights_generator/  # SemanticInsights tests
│   ├── __init__.py
│   └── test_e2e.py
└── conftest.py

All tests verified passing after reorganization.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: leonidb

tests/agentune/analyze/feature/gen/conftest.py

@@ -2,8 +2,8 @@
 
 import pytest
 
-# Import fixtures from test_e2e.py to make them available to all tests in this directory
-from tests.agentune.analyze.feature.gen.test_e2e import (
+# Import fixtures from insightful_text_generator tests to make them available to all tests
+from tests.agentune.analyze.feature.gen.insightful_text_generator.test_e2e import (
     problem,
     real_llm_with_spec,
     test_dataset_with_strategy,

tests/agentune/analyze/feature/gen/insightful_text_generator/__init__.py

@@ -0,0 +1 @@
+"""Tests for InsightfulTextGenerator (ConversationQueryFeatureGenerator)."""