docs: refresh stale file paths after store/ reorg + gen_messages rename

generate_messages.py → gen_messages.py and several gem/ headers moved
under gem/store/ (carrier_store.hpp → store/carriers.hpp, etc.);
e84.hpp split into e84_state.hpp.  The guided-tour chapters still
pointed at the old paths — relink them so the deep-link footnotes
resolve.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

docs/40_building_running_demo.md

@@ -319,8 +319,10 @@ docker compose run --rm builder tshark -i any -d "tcp.port==5000,hsms" -V \
 `pvd_tool` example exposes a Prometheus endpoint:
 
 ```bash
-docker run --rm -p 9090:9090 pvd_tool /app/examples/pvd_tool/equipment.yaml \
-    /app/data/control_state.yaml 5000 9090
+docker compose run --rm --service-ports builder /app/build/pvd_tool \
+    /app/examples/pvd_tool/equipment.yaml \
+    /app/data/control_state.yaml \
+    5000 9090
 ```
 
 Then `curl localhost:9090/metrics`.