A "Plan" panel, opened from Track layout in the editor's menu bar, draws a
niweleta the way the web frontend did: click to lay chained straights, drag
a corner to move it, and pick a fit for each gap between them. The geometry
is entirely maj0sted's - the panel gathers the input, hands the document to
solve_project and paints the rails that come back, coloured by whether they
came from a straight, an arc or a clothoid. Scenery nodes are untouched.
A fit the library cannot produce is simply absent from its answer, so the
gap is labelled as not fitting rather than left looking as though its
parameters took effect. Save/load go through the library's own document
format, so a project written here opens in the same state.
Also translates the comments added with -editor into English, matching the
files they sit in.
The editor was reachable only from the driver mode with F11, which meant
loading a scenario and starting the whole simulation first. With -editor
the scenario loader hands over to the editor instead of the driver, so
physics, AI and timetables never run - only the loaded world is there to
be worked on.
Without -s the scenery from eu07.ini is used, falling back to pusta.scn
when the ini names none. F11 quits instead of popping the mode, since the
editor is now the bottom of the mode stack and popping it would leave the
rest of the frame reading an empty one. Editor entry forces free-fly even
with no vehicle to leave.
Consolidates platform-specific config-directory logic (APPDATA on Windows,
~/Library/Application Support on macOS, ~/.config on Linux) into a single
user_config_path(filename) function in utilities/utilities.{cpp,h}, removing
copy-pasted #ifdef blocks from application.cpp, editor/editorSettings.cpp,
input/{keyboard,gamepad,drivermouse,uart}input.cpp.
