Add official library demo catalog

[suguanYang]

Summary

• add an Official Library catalog on top of the existing Knowhere demo-source/materialization flow
• add staging-parsed demo bundles for 17 new ready library documents plus existing SpaceX, while leaving 4 failed/unsupported URLs planned
• extend demo-document validation and contract coverage for official-library categories, ready links, and planned items

Ready documents

• SpaceX S-1, NVIDIA Q1/Q4 materials, NVIDIA FY26 annual report, GOOG 10-K, Meta Q1 materials, Microsoft 2025 annual report, Alibaba FY2026 interim report
• STEM: Stanford/Jurafsky Transformers, Deep Learning Transformer Network, Probability Theory notes, Statistical Learning notes, Introduction to Statistical Learning Theory

Planned after staging parse failures

• both Micron static-file URLs: staging job creation timed out repeatedly
• AIHub Transformers tutorial: staging failed to download the URL
• Information Theory: 730 pages exceeded direct processing and shard planning failed

Verification

• Knowhere CLI staging parse batch with provided key (redacted from logs/messages)
• S3_BUCKET_NAME=test S3_ACCESS_KEY_ID=test S3_SECRET_ACCESS_KEY=test S3_TEMP_PATH=/tmp DATABASE_URL=postgresql://postgres:postgres@127.0.0.1:5432/postgres TMP_PATH=/tmp uv run python apps/api/scripts/validate_demo_documents.py
• uv run pytest apps/api/tests/contract/test_demo_documents_contract.py -q
• uv run ruff check apps/api/app/services/demo/official_library_catalog.py apps/api/app/services/demo/source_catalog.py apps/api/scripts/validate_demo_documents.py apps/api/tests/contract/test_demo_documents_contract.py
• uv run pyright apps/api/app/services/demo/official_library_catalog.py apps/api/app/services/demo/source_catalog.py apps/api/scripts/validate_demo_documents.py apps/api/tests/contract/test_demo_documents_contract.py