fix: resolve relative input paths given on the command line (#14803)

Opening a model with a relative path, for example `orca-slicer ./some.3mf`,
failed with "Loading of a model file failed." and "The file does not contain
any geometry data.", while the same file opened by an absolute path or by
drag and drop worked.

GUI_App::init_app_config() changes the working directory to <data_dir>/log,
and it runs from the GUI_App constructor because the app config is needed
early for instance checking. The input files are opened much later, in
post_init(), so a path still relative at that point resolved against the log
directory instead of the directory OrcaSlicer was started from, and the 3MF
reader failed to open it.

Resolve the input paths in CLI::setup(), which runs before GUI_App is
constructed and therefore before the working directory moves. Absolute paths
are returned unchanged, so the forms that open today are unaffected, and
custom open protocol URLs are passed through since post_init() hands those to
the downloader rather than the file loader.

The working directory change is left alone. It was added in #3248 so the TUTK
logs land in the data directory instead of the working directory (#3209).

src/libslic3r/Utils.hpp

@@ -314,6 +314,9 @@ extern unsigned get_current_pid();
 std::string per_user_temp_id();
 // Per-user temp root under `base`; an empty `user_id` returns `base` unchanged.
 std::string per_user_temp_dir(const std::string &base, const std::string &user_id);
+// Completes a relative command line input path against the current working directory. Absolute
+// paths and custom open protocol URLs are returned unchanged.
+std::string resolve_cli_input_path(const std::string &path);
 // BBS: backup & restore
 std::string get_process_name(int pid);
 

src/libslic3r/utils.cpp

@@ -1339,6 +1339,19 @@ std::string per_user_temp_dir(const std::string &base, const std::string &user_i
     return base + "/orcaslicer_" + user_id;
 }
 
+std::string resolve_cli_input_path(const std::string &path)
+{
+    const boost::filesystem::path input(path);
+    if (path.empty() || is_supported_open_protocol(path) || input.is_absolute())
+        return path;
+
+    boost::system::error_code ec;
+    const boost::filesystem::path resolved = boost::filesystem::system_complete(input, ec);
+    if (ec)
+        return path;
+    return resolved.lexically_normal().make_preferred().string();
+}
+
 // BBS: backup & restore
 std::string get_process_name(int pid)
 {