wx: run scripts at boot via the engine (--source / --batch)

Now that core has run_script, wire WxFrontend::BootDispatch's `source` to it
instead of the "no script interpreter" note. `essim --source bring-up.essim`
(and with --batch) now executes the script in the wx frontend too, accumulating
the same output the tui produces into the console buffer surfaced by DumpOutput.

Verified: `essim --batch --source script.essim` (wx) runs load + set-signal-type
+ verify and prints the source summary.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/frontends/wx/wx_frontend.cpp

@@ -2,6 +2,7 @@
 
 #include "frontends/wx/wx_frame.hpp"
 
+#include "core/app/script.hpp"
 #include "core/domain/connect.hpp"
 #include "core/domain/modules.hpp"
 #include "core/domain/persist.hpp"
@@ -74,8 +75,15 @@ void WxFrontend::BootDispatch(const std::string &raw) {
                  + std::to_string(sys_->connections()->size())
                  + " connection(s))\n";
     } else if (cmd == "source") {
-        output_ += "source: the wx frontend has no script interpreter "
-                   "(use the tui frontend for scripts).\n";
+        ensure_system();
+        std::ostringstream out;
+        app::ScriptResult r = app::run_script(sys_, arg, out);
+        output_ += out.str();
+        if (!r.ok)
+            output_ += "source: " + r.error + "\n";
+        else
+            output_ += "source: " + arg + "  (" + std::to_string(r.lines)
+                     + " line(s), " + std::to_string(r.errors) + " error(s))\n";
     } else if (!cmd.empty()) {
         output_ += "boot: ignored '" + raw + "'.\n";
     }