fix(task-18): the COM plot is foreground, by layout name, and confirmed on disk; plot_style_list reads PrinterStyleSheetPath

Three review findings against SECTION 19 on the live engine, each measured
on AutoCAD 2026 in a scratch document with the operator's BACKGROUNDPLOT=2:

- plot_style_list read Preferences.Files.PrintStyleSheetPath; the ActiveX
  member is PrinterStyleSheetPath, so the AttributeError was swallowed and
  every row came back installed=None. Renamed in the backend, the server
  docstring and the test fake (which faked the same wrong name). Live: 13
  rows, all 9 catalogue ctb files installed, four .stb files as installed.
- ComBackend.drawing_export_pdf returned ok before any file existed under
  background plotting, so batch_plot died on path.stat() with an unhandled
  FileNotFoundError and a later foreground plot raised E_FAIL. The export
  now sets BACKGROUNDPLOT=0 around PlotToFile (restored after), honours the
  method's bool and reports ok only with the file on disk (bytes included).
  batch_plot turns a backend RuntimeError or a phantom ok into a per-row
  ok:false, keeping the rows already plotted.
- With a sheet current, the Model row was that sheet plotted again: the COM
  export switched tabs only when a layout was named. layout=None now makes
  Model current (restoring the tab), and batch_plot names every layout,
  Model included, so both engines plot the tab the row is labelled with.
  Live: Model row /Title (Model) at 210x297 beside the A3 sheet, the active
  tab and BACKGROUNDPLOT restored.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FKFStjEFzpGyLq5bMpWxTd

engineering/standards/plot.py

@@ -36,7 +36,10 @@ async def batch_plot(
     """Plot layouts to PDF and read each sheet size back from the file.
 
     ``layouts=None`` plots every paper-space layout; ``Model`` is plotted only
-    when named. Refuses (``ValueError``, before any PDF is written): an empty
+    when named, and is passed to the engine by name so the model row is model
+    space whichever tab is current. A sheet the engine cannot plot, or reports
+    plotted without a file, is a per-row ``ok: False`` with its ``error``; the
+    rows before it stay. Refuses (``ValueError``, before any PDF is written): an empty
     list, a layout that does not exist, a pattern with a path separator, and
     a pattern without ``{layout}`` when more than one sheet would be written.
     The output folder is created, then every output path goes through
@@ -95,12 +98,31 @@ async def batch_plot(
     sheets: list[dict] = []
     for name, path in planned:
         is_model = name.lower() == "model"
-        result = await backend.drawing_export_pdf(str(path), layout=None if is_model else name)
+        # The layout is always named — "Model" included — so the engine plots
+        # the tab this row is labelled with, never the one that happens to be
+        # current. A plot that fails inside the engine (COM raises RuntimeError
+        # for an AutoCAD error) or that reports ok without leaving a file is a
+        # failed row, not a lost batch: the sheets already plotted are kept.
+        try:
+            result = await backend.drawing_export_pdf(str(path), layout=name)
+        except RuntimeError as exc:
+            sheets.append({"layout": name, "ok": False, "path": str(path), "error": str(exc)})
+            continue
         if not result.get("ok", False):
             sheets.append(
                 {"layout": name, "ok": False, "path": str(path), "error": result.get("error")}
             )
             continue
+        if not path.is_file():
+            sheets.append(
+                {
+                    "layout": name,
+                    "ok": False,
+                    "path": str(path),
+                    "error": "the engine reported the plot ok but no file was written",
+                }
+            )
+            continue
         row = {"layout": name, "ok": True, "path": str(path), "bytes": path.stat().st_size}
         try:
             width, height = read_mediabox(str(path))