Extract duplicate into core; support it in the script engine + wx GUI

A script using `duplicate` failed with "unsupported command 'duplicate'"
because the clone logic was still inline in the tui command. Extract it to
core/app/edit.hpp::duplicate_module(System*, src, dst) -> {ok, error, parts,
signals}: a deep clone of a module (parts, pins with spec + nc_origin, signals
with type overrides, pin→signal wiring; no connections), refusing on an unknown
source or an already-taken destination name.

  - the tui `duplicate` command renders the result (output unchanged);
  - the script engine dispatches `duplicate` to it — the failing script now runs;
  - the wx GUI gains Edit ▸ Duplicate module… (PickModule + a name prompt).

tests/test_edit.cpp: deep clone wires to the clone's own signal (not the
source's) and preserves the type; unknown source / existing destination
refused. 412 core assertions green; tui + wx build clean.

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

src/core/app/edit.hpp

@@ -7,6 +7,7 @@
 
 class Part;
 class Signal;
+class System;
 
 // Application layer: UI-independent part-editing operations any frontend can
 // call. No console, no dialogs, no FTXUI — Part in, result struct out.
@@ -52,6 +53,21 @@ struct SetSignalTypeResult {
 // Fails (ok=false, error set, no mutation) on an unrecognised name.
 SetSignalTypeResult set_signal_type(Signal *sig, const std::string &type_name);
 
+// Outcome of cloning a module under a new name.
+struct DuplicateResult {
+    bool ok = false;
+    std::string error;  ///< unknown source, or destination name already taken
+    int parts = 0;
+    int signals = 0;
+};
+
+// Deep-clone module `src_name` as `dst_name`: parts, pins (spec + nc_origin),
+// signals (with type overrides) and the pin→signal wiring — but not the
+// system's connections. Fails (ok=false, error set, no change) when the source
+// is unknown or the destination name already exists.
+DuplicateResult duplicate_module(System *sys, const std::string &src_name,
+                                 const std::string &dst_name);
+
 }  // namespace app
 
 #endif  // _APP_EDIT_HPP_