drb 2.9.0: multi-file topic descriptors via the cortex_paths() protocol. A drb.topic entry-point module may expose cortex_paths() returning the paths of several descriptor files; the loader merges them all into the shared topic graph. Single-file cortex.ttl/cortex.owl discovery is unchanged. Implements drb-testbench#15 (loader side); first consumers are the drbx-kb-metadata-* packages (drb-testbench#40 phase 1).