…(LOC-63)

PR5 (hygiene), backend-agnostic.

N6: HNSW index-build paths decoded embeddings with
decode_f32_embedding(..).unwrap_or_default(), turning a corrupt blob into
an empty Vec that the !is_empty() filter then dropped silently. Add
decode_f32_embedding_or_warn(blob, row_id): logs a warning (with row id)
on failure and returns an empty Vec, so behaviour is preserved (still
dropped) but corruption is visible. Dedups the pattern across the 6 sites
(simple_rag, source_rag).

N5 (conservative): document the native-endian / little-endian storage
assumption and the alignment reason zero-copy decode is unsound, on
decode_f32_embedding. No format change (all targets are LE); full
normalization + a shared encode helper left as backlog.

Journal: PR5.md, README (PR3 보류 / PR4 폐기 / PR5 진행), risk-register
R7+N6 closed, and RETRO.md (final retrospective).