docs(retrieval): align score_propagation_alpha default 0.5→1.0 with #1947

[r266-tech]

Summary

Aligns documentation with #1947 (qin-ptr/qin-ctx 2026-05-09T11:58Z), which changed RetrievalConfig.score_propagation_alpha default from 0.0 to 1.0 in openviking_cli/utils/config/retrieval_config.py. Five docs/example files still showed 0.5 (the original pre-#1804 default), creating drift two steps behind code.

Changes

Default value 0.5 → 1.0 and description rewording so the canonical-anchor case is the new default:

• docs/en/guides/01-configuration.md — retrieval JSON example, table row description+default, Full Schema appendix JSON example
• docs/zh/guides/01-configuration.md — mirror of above
• examples/ov.conf.example — single-line retrieval block
• docs/en/concepts/07-retrieval.md — Key Parameters row in Hierarchical Retrieval section
• docs/zh/concepts/07-retrieval.md — mirror of above

Description text reordered to put 1.0 first ("ignores the parent score (semantic similarity only)") so the explanatory anchor matches the actual default. Prior text said "0.5 keeps the existing equal blend" — that "existing" framing referenced 0.5 as default, which is no longer true. 0.5 and 0.0 retained as alternative-behavior callouts.

Notes

• Tests not touched: tests/test_config_loader.py asserts 0.5 from a fixture .conf (explicit value, not the model default); tests/retrieve/test_hierarchical_retriever_rerank.py already exercises RetrievalConfig(score_propagation_alpha=1.0) directly. Both remain valid.
• Out of scope: openviking/eval/datasets/local_doc_example_glm5.jsonl mentions SCORE_PROPAGATION_ALPHA = 0.5 inside a static training-data answer string. Left alone.
• Diff size: 9 line edits across 5 files, 0 deletions of unrelated content.

cc @qin-ctx — fresh follow-up to your #1947 merge.

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🎫 Ticket compliance analysis ✅ 1947 - Fully compliant Compliant requirements: Align documentation with retrieval_config.py's score_propagation_alpha default of 1.0

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