Merge pull request #383 from KevinGriffin-new/fix/pdf-export

Never fail silently on PDF export; add EXPORTPDF <path> (#369).

The export flow handed off to an async rfd save dialog and mapped a None
result straight to Task::none(). On Linux None also means the dialog never
opened (broken XDG portal / missing zenity), and rfd reports that only via
log, so PDF export could end in total silence. The dialog-None arms now
print a message pointing at EXPORTPDF <path>, and EXPORT/EXPORTPDF take an
optional path that exports straight to a file with no dialog — the
workaround where the native dialog can't open, and a headless entry point.

Conflict: the fix (display.rs, file.rs, mod.rs, COMMANDS.md) auto-merged;
only the additive test block in automation.rs conflicted. Resolved by
keeping main's tests and adding the two #369 tests.

# Conflicts:
#	src/app/automation.rs

src/app/update/mod.rs

@@ -3582,7 +3582,18 @@ impl OpenCADStudio {
                     Message::PlotExportPath,
                 )
             }
-            Message::PlotExportPath(None) => Task::none(),
+            // None means the save dialog was cancelled — or never opened at
+            // all (a broken XDG portal / missing zenity on Linux resolves to
+            // None too, and rfd only reports that through `log`, which is
+            // opt-in). Either way say something instead of silently doing
+            // nothing. (#369)
+            Message::PlotExportPath(None) => {
+                self.command_line.push_info(
+                    "PDF export canceled — no file chosen. \
+                     If no dialog appeared, use EXPORTPDF <path>.",
+                );
+                Task::none()
+            }
             Message::PlotExportPath(Some(path)) => self.on_plot_export_path_some(path),
 
             Message::PlotFormat(f) => {
@@ -3606,7 +3617,14 @@ impl OpenCADStudio {
                     Message::PlotWindowExportPath,
                 )
             }
-            Message::PlotWindowExportPath(None) => Task::none(),
+            // Same silent-None trap as PlotExportPath above. (#369)
+            Message::PlotWindowExportPath(None) => {
+                self.command_line.push_info(
+                    "PDF export canceled — no file chosen. \
+                     If no dialog appeared, use EXPORTPDF <path>.",
+                );
+                Task::none()
+            }
             Message::PlotWindowExportPath(Some(path)) => self.on_plot_window_export_path_some(path),
 
             // ── Print to system printer ───────────────────────────────────────