Editor checkpoint: turnout domain service, web->editor rename, Id-1 templates

Checkpoint of the editor branch so work isn't carried loose across a branch
switch. Builds.

- maj0sted turnout geometry moved into the domain: domain::lay_turnout lays the
  diverging path (pre-blade lead, blade at beta, arc of alfa-beta, frog rail) and
  solve_junction is a thin adapter onto it.
- the maj0sted web/ tree renamed to editor/ (namespace and paths) - there is no
  WASM here, it's plain native C++ the editor calls.
- click places the switch at its start (początek rozjazdu); the branch's leaving
  straight is locked tangent to the frog; switches can be slid along the through
  track and flipped L/P.
- Polish turnout templates carry catalogue length (Id-1-consistent lengths), plus
  blade-angle and pre-blade fields (left 0 until the catalogue figures are in).
- TURNOUT_SPEC.md: the Bezier-based runtime/model contract.
- also folds in other pending branch changes (scenery, tests) to leave a clean tree.

application/scenarioloadermode.cpp

@@ -53,12 +53,17 @@ bool scenarioloader_mode::update() {
 	}
 	catch (invalid_scenery_exception &e) {
 		ErrorLog( "Bad init: scenario loading failed" );
+		state.reset();
 		Application.pop_mode();
 	}
 
 	WriteLog( "Scenario loading time: " + std::to_string( std::chrono::duration_cast<std::chrono::seconds>( std::chrono::system_clock::now() - timestart ).count() ) + " seconds" );
 	// TODO: implement and use next mode cue
 
+	// the mode object is kept for the next time a scenery is loaded; without dropping the context
+	// here, a later enter() would skip deserialize_begin and finish an already-spent parser again
+	state.reset();
+
 	Application.pop_mode();
 	// starting into the editor the simulation never runs at all: there's no driver mode underneath, so
 	// no physics, no AI and no timetables - just the loaded world to work on
@@ -79,6 +84,11 @@ void scenarioloader_mode::enter() {
     // TBD: hide cursor in fullscreen mode?
     Application.set_cursor( GLFW_CURSOR_NORMAL );
 
+    // a new map from the editor re-enters this mode while the previous load's context is still
+    // sitting in `state`; clear it so update() opens the file again instead of re-finishing an
+    // exhausted parser (Groups.close / create_map_geometry on an already-built region)
+    state.reset();
+
     simulation::is_ready = false;
 
     Application.set_title( Global.AppName + " (" + Global.SceneryFile + ")" );