Corpus hygiene + coverage batch: drop amendment stubs, add 8 instruments, currency & guidance fixes

Expand corpus: add 10 in-scope primary-law instruments (Phase 1)

Add the public-service benefit-plan member booklets (new doc_type 'benefits')

Use case-law topic, not paragraph range, as the retrieval title

Add 10 leading SCC and FC decisions

Ingest Customs Tariff Schedule Chapters 98 and 99

Add IRPA delegation instruments, R. v. Carignan, and retrieval polish

Add Phase 4 case law: 23 FPSLREB and CIRB labour-board decisions

Expand eval set to 89 questions; add semantic-fusion weight knob

Upgrade retrieval: bge-small embeddings + promote-only reranking