idea2story_pipeline.py keeps failing novelty index check even after successful rebuild

[ruizhengu]

Running idea2story_pipeline.py fails with a novelty index error, even though build_novelty_index.py reports a successful build.

Steps to Reproduce

1. Run the main pipeline:
   python Paper-KG-Pipeline/scripts/idea2story_pipeline.py "idea"
   Output:
   ❌ 错误: Novelty index build failed or incomplete. Please run build_novelty_index.py manually. Traceback (most recent call last): File "/Idea2Paper/Paper-KG-Pipeline/scripts/idea2story_pipeline.py", line 348, in main ensure_required_indexes(logger) File "/Idea2Paper/Paper-KG-Pipeline/scripts/idea2story_pipeline.py", line 224, in ensure_required_indexes raise RuntimeError("Novelty index build failed or incomplete. Please run build_novelty_index.py manually.") RuntimeError: Novelty index build failed or incomplete. Please run build_novelty_index.py manually.
2. Build the novelty index:
   python Paper-KG-Pipeline/scripts/tools/build_novelty_index.py
   Output:
   ✅ Index already exists. Use --force-rebuild to rebuild.
   Force-rebuild the novelty index:
   python Paper-KG-Pipeline/scripts/tools/build_novelty_index.py --force-rebuild
   Output:
   ✅ Build done. index_count=1501, skipped=6784 index_dir=/Idea2Paper/Paper-KG-Pipeline/output/novelty_index__voyage-4
3. Run the main pipeline again:
   python Paper-KG-Pipeline/scripts/idea2story_pipeline.py "idea"
   Output:
   ❌ 错误: Novelty index build failed or incomplete. Please run build_novelty_index.py manually. Traceback (most recent call last): File "/Idea2Paper/Paper-KG-Pipeline/scripts/idea2story_pipeline.py", line 348, in main ensure_required_indexes(logger) File "/Idea2Paper/Paper-KG-Pipeline/scripts/idea2story_pipeline.py", line 224, in ensure_required_indexes raise RuntimeError("Novelty index build failed or incomplete. Please run build_novelty_index.py manually.") RuntimeError: Novelty index build failed or incomplete. Please run build_novelty_index.py manually.

Expected Behaviour

After successfully building (or force-rebuilding) the novelty index, idea2story_pipeline.py should detect the existing index and proceed without raising RuntimeError.

Actual Behavior

idea2story_pipeline.py always raises:
RuntimeError: Novelty index build failed or incomplete. Please run build_novelty_index.py manually.

Environment:

OS: macOS 26.2
Python version: 3.11.14

[ruizhengu]

I've opened a PR for fixing this: #42