feat(clients)+test(interop): C++ client + Java validation of the daemon (B7)

B7 — the daemon's HSMS face under the Java reference: Dockerfile.server now
bakes secs_gemd alongside secs_server (grpc deps in both stages), and
secs4j_validate.sh gains TARGET=gemd to point the 55-check secs4java8 suite
at the daemon instead. Result: 55/55 green. With secsgem-py already
validating both faces, byte-identical GEM between secs_server and secs_gemd
is now proven by both reference implementations, not inferred from shared
code. CI runs the daemon target as an extra step (image layers shared).

Second client — clients/cpp: a header-only C++ twin of the Python client
over the same proto. eq.set("ChamberPressure", 2.5) with bare literals
(integral/floating dispatch avoids variant ambiguity), get/fire/alarm/
clear, control_state/request_control_state/health, on("START", fn) +
listen()/listen_async()/stop() with auto-CompleteCommand, SecsGemError
carrying the daemon's message. cpp_mini_tool (~30 lines) mirrors the
Python mini_tool. Tested end-to-end over real loopback TCP against the
service inside secs_gemd_tests — now 4 cases / 141 assertions — including
set/get round-trips, error text, alarm-by-name into the model, health,
and the full HCACK-4 command loop with parameters.

(Build note: two grpc-heavy TUs at -O3 OOM even at -j2 on Docker Desktop;
built -j1. Known environment limitation, roadmap-documented.)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

.gitea/workflows/ci.yml

@@ -201,6 +201,12 @@ jobs:
       - name: secs4j cross-validation
         run: bash interop/secs4j_validate.sh
 
+      # Same 55 Java checks against the DAEMON's HSMS face: secs_gemd and
+      # secs_server both sit on register_default_handlers, so they must be
+      # byte-identical GEM. Image layers are shared with the step above.
+      - name: secs4j cross-validation (secs_gemd)
+        run: TARGET=gemd bash interop/secs4j_validate.sh
+
   python-interop:
     # secsgem-py (the Python reference implementation) judging our wire
     # behaviour: its GemHostHandler drives our secs_server (31 checks), the