fix(lint): revert redundant Write conversion (staticcheck S1016)

writeRequest and WriteNoteOptions have matching fields again now that
both carry SourceType, so the explicit field-by-field literal added
in ee1204d is flagged as a redundant conversion. Back to the plain
type conversion. Caught by task check (golangci-lint), not run
locally before the previous push -- plain go test passed, task check
(which adds -race and golangci-lint) didn't.

ingestion/internal/api/handler.go

@@ -240,15 +240,7 @@ func (h *Handler) Write(w http.ResponseWriter, r *http.Request) {
 		writeError(w, http.StatusBadRequest, "invalid JSON")
 		return
 	}
-	relPath, err := WriteNote(h.brainDir, WriteNoteOptions{
-		Content:    req.Content,
-		Filename:   req.Filename,
-		Type:       req.Type,
-		Domain:     req.Domain,
-		Wing:       req.Wing,
-		Hall:       req.Hall,
-		SourceType: req.SourceType,
-	})
+	relPath, err := WriteNote(h.brainDir, WriteNoteOptions(req))
 	if err != nil {
 		h.logger.Error("write failed", "err", err)
 		writeError(w, http.StatusBadRequest, err.Error())