B3: HostHandler RCMD/alarm/recipe/terminal/job senders

Fleshes out the host-side message surface so the demo client app no
longer has to inline message construction.  Senders added (each is a
one-line wrapper over the codegen builders + Connection::send_request):

  Remote command:    S2F41/F42, S2F49/F50
  Alarm management:  S5F3/F4 enable, S5F5/F6 list, S5F7/F8 list-enabled,
                     S5F13/F14 recover, S5F17/F18 recover-abort
  Process programs:  S7F3/F4 send, S7F5/F6 request, S7F19/F20 EPPD
  Spool:             S6F23/F24
  Terminal:          S10F1/F2 single, S10F5/F6 multi
  E40 Process Jobs:  S16F11/F12 create, S16F5/F6 command, S16F13/F14 dequeue
  E94 Control Jobs:  S14F9/F10 create, S14F11/F12 delete, S16F27/F28 command

CommandParameter is reused from store/host_commands.hpp rather than
inventing a parallel ParamPair — host and equipment talk in the same
struct now.

Closes the outbound side of the host-mode menu.  The remaining piece
is an integration test that drives this against the equipment server
end-to-end (B4).

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

include/secsgem/gem/host_handler.hpp

@@ -9,7 +9,10 @@
 #include <vector>
 
 #include "secsgem/gem/store/event_reports.hpp"
+#include "secsgem/gem/store/host_commands.hpp"  // CommandParameter
+#include "secsgem/gem/store/spool.hpp"          // SpoolRequestCode
 #include "secsgem/hsms/connection.hpp"
+#include "secsgem/secs2/item.hpp"
 #include "secsgem/secs2/message.hpp"
 
 // GEM host-side message handler.  Wraps an HSMS Connection (Active mode)
@@ -96,6 +99,70 @@ class HostHandler : public std::enable_shared_from_this<HostHandler> {
   void send_enable_events(bool enable, const std::vector<uint32_t>& ceids,
                           ReplyHandler cb);
 
+  // ---- Remote command senders (B3) --------------------------------------
+
+  // S2F41/F42 Host Command.  `params` reuses CommandParameter from
+  // host_commands.hpp so host- and equipment-side code share the type.
+  void send_remote_command(const std::string& rcmd,
+                           const std::vector<CommandParameter>& params,
+                           ReplyHandler cb);
+
+  // S2F49/F50 Enhanced Host Command (OBJSPEC-scoped + per-CP CPACK/CEPACK).
+  void send_enhanced_remote_command(uint32_t dataid, const std::string& objspec,
+                                    const std::string& rcmd,
+                                    const std::vector<CommandParameter>& params,
+                                    ReplyHandler cb);
+
+  // ---- Alarm management (B3) --------------------------------------------
+
+  // S5F3/F4 Enable/Disable Alarm.  Spec uses ALED bit-7 to encode enable.
+  void send_enable_alarm(uint32_t alid, bool enable, ReplyHandler cb);
+  void send_list_alarms(const std::vector<uint32_t>& alids, ReplyHandler cb);  // S5F5/F6
+  void send_list_enabled_alarms(ReplyHandler cb);                              // S5F7/F8
+
+  // S5F13/F14 Exception Recover Request.  Asks the equipment to perform
+  // the named recovery action against the previously-posted EXID.
+  void send_exception_recover(uint32_t exid, const std::string& exrecvra,
+                              ReplyHandler cb);
+  void send_exception_recover_abort(uint32_t exid, ReplyHandler cb);  // S5F17/F18
+
+  // ---- Process program transfer (B3) ------------------------------------
+
+  void send_request_eppd(ReplyHandler cb);                                       // S7F19/F20
+  void send_pp_data(const std::string& ppid, const std::string& body,
+                    ReplyHandler cb);                                            // S7F3/F4
+  void send_request_pp(const std::string& ppid, ReplyHandler cb);                // S7F5/F6
+
+  // ---- Spool (B3) -------------------------------------------------------
+
+  void send_request_spool(SpoolRequestCode code, ReplyHandler cb);  // S6F23/F24
+
+  // ---- Terminal (B3) ----------------------------------------------------
+
+  void send_terminal_display(uint32_t tid, const std::string& text,
+                             ReplyHandler cb);                                   // S10F1/F2
+  void send_terminal_display_multi(uint32_t tid,
+                                   const std::vector<std::string>& lines,
+                                   ReplyHandler cb);                             // S10F5/F6
+
+  // ---- E40 Process Jobs (B3) --------------------------------------------
+
+  void send_create_process_job(const std::string& prjobid, const std::string& ppid,
+                               const std::vector<std::string>& mtrloutspec,
+                               ReplyHandler cb);                                 // S16F11/F12
+  void send_pr_job_command(const std::string& prjobid, const std::string& prcmd,
+                           ReplyHandler cb);                                     // S16F5/F6
+  void send_pr_job_dequeue(const std::string& prjobid, ReplyHandler cb);         // S16F13/F14
+
+  // ---- E94 Control Jobs (B3) --------------------------------------------
+
+  void send_create_control_job(const std::string& ctljobid,
+                               const std::vector<std::string>& prjobids,
+                               ReplyHandler cb);                                 // S14F9/F10
+  void send_delete_control_job(const std::string& ctljobid, ReplyHandler cb);    // S14F11/F12
+  void send_cj_command(const std::string& ctljobid, const std::string& ctljobcmd,
+                       ReplyHandler cb);                                         // S16F27/F28
+
   // ---- Low-level: forward a primary verbatim ----------------------------
   void send_request(secs2::Message msg, ReplyHandler cb);