ODS import, persistence, scripting, connector types + VPX transforms.

- ODS importer (libzip + pugixml): each sheet → Part, rows → Pin/Signal.
- save / restore commands: tab-delimited snapshot of modules, parts,
  signals, connections + pin_map. `restore` replaces the System.
- source / script-save: replay a file of commands; record canonical
  commands since last `new` for replay later. Interactive screens
  refused during source. `explore` marked non-scriptable.
- TUI screen_explore: 4 columns (modules, type, children, detail) with
  filters on children and detail; detail is a Menu so arrows scroll
  long pin lists.
- Connector types & transforms: each Part carries a `connector_type`
  string. `set-type` validates the part's pin layout against the type
  (cols set check). `connect` strict pair: rejects when lookup falls
  back to identity unless types are both empty AND pin sets match.
- VPX 3U transforms: 3 registered pairs (vpx-3u-bkp-pN ↔ vpx-3u-payload-pN,
  N=0/1/2) with row-pattern correspondence tables ported from the user's
  Python reference.
- Code split for maintainability: src/tui/{shell,completion,commands,
  screen_main,screen_search,screen_connect,screen_settype,screen_explore,
  tui_helpers}.cpp.
- Bug fixes: Module::add(Part*) override sets part->prnt (was always
  null, breaking save's W lines). Defensive guards in explore against
  empty Menu lists. Renderer wrapped in try/catch so domain throws
  surface as on-screen errors instead of SIGABRT.

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

CMakeLists.txt

@@ -23,6 +23,9 @@ FetchContent_Declare(ftxui
 )
 FetchContent_MakeAvailable(ftxui)
 
+find_package(libzip REQUIRED)
+find_package(pugixml REQUIRED)
+
 file(GLOB_RECURSE ALL_SOURCES "src/*.cpp")
 
 add_executable(essim ${ALL_SOURCES})
@@ -34,4 +37,6 @@ target_link_libraries(essim
     ftxui::screen
     ftxui::dom
     ftxui::component
+    libzip::zip
+    pugixml::pugixml
 )