feat(pipeline): add POST /ingest-raw for direct batch ingestion without LLM

Allows callers to provide pre-structured RawPage data directly, bypassing the
LLM extraction step. The pipeline still handles slug computation, frontmatter,
link canonicalization, source back-references, and dedup — only the extraction
is skipped. Useful when a more capable model or manual curation produces the
structured data.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ingestion/cmd/server/main.go

@@ -68,6 +68,7 @@ func main() {
 	mux.HandleFunc("POST /write", h.Write)
 	mux.HandleFunc("POST /ingest", h.Ingest)
 	mux.HandleFunc("POST /ingest-path", h.IngestPath)
+	mux.HandleFunc("POST /ingest-raw", h.IngestRaw)
 	mux.HandleFunc("POST /backfill-refs", h.BackfillRefs)
 
 	addr := ":" + port