feat(pagesetup): page_setup_list/apply on both engines — the PDF's own /MediaBox is the evidence

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

backends/contracts/__init__.py

@@ -21,6 +21,7 @@ from backends.contracts.identity import IdentityContract
 from backends.contracts.layers import LayerContract
 from backends.contracts.layouts import LayoutContract
 from backends.contracts.linetypes import LinetypeContract
+from backends.contracts.pagesetup import PageSetupContract
 from backends.contracts.premium import PremiumContract
 from backends.contracts.settings import SettingsContract
 from backends.contracts.solids import SolidContract
@@ -42,6 +43,7 @@ __all__ = [
     "LayerContract",
     "LayoutContract",
     "LinetypeContract",
+    "PageSetupContract",
     "PremiumContract",
     "SettingsContract",
     "SolidContract",

backends/contracts/pagesetup.py

@@ -0,0 +1,59 @@
+"""Page setup, plot styles and templates (v1.6 track E, group P).
+
+``AutoCADBackend`` composes every contract in this package, so importing
+``backends.base.AutoCADBackend`` is unchanged for callers.
+"""
+
+from __future__ import annotations
+
+from abc import ABC, abstractmethod
+
+
+class PageSetupContract(ABC):
+    @abstractmethod
+    async def page_setup_list(self, layout: str | None = None) -> list[dict]:
+        """Page setup of one paper-space layout, or of every one.
+
+        Rows: ``{layout, paper, canonical_media_name, size_mm: [w, h],
+        orientation, plot_style, scale, plot_area, device,
+        margins_mm: [top, bottom, left, right], center}``. ``paper`` is the
+        catalogue name when the size matches one within 0.5 mm, otherwise the
+        media name as stored. Raises ``ValueError`` for an unknown layout.
+        ``Model`` is never listed: model space is plotted through
+        ``drawing_export_pdf(layout=None)`` and carries no sheet.
+        """
+        ...
+
+    @abstractmethod
+    async def page_setup_apply(self, layout: str, setup: dict) -> dict:
+        """Write a page setup resolved by
+        ``engineering.standards.papers.resolve_page_setup`` to a layout.
+
+        Returns ``{ok, layout, applied: {...setup}, changed: {key: [old, new]},
+        plot_style_known, viewports_kept}``. ``changed`` is computed from the
+        read-back before and after, so re-applying the same setup reports
+        ``{}``. Refuses ``Model``, an unknown layout, and a ``setup`` missing a
+        resolved key, before anything is written. Never deletes viewports.
+        """
+        ...
+
+    @abstractmethod
+    async def plot_style_list(self) -> list[dict]:
+        """``[{name, source: "catalog"|"installed", installed: bool|None}]`` —
+        the authored ctb catalogue plus, on a live engine, the files present
+        in the plot style search path. ``installed`` is ``None`` where no
+        installation can be scanned."""
+        ...
+
+    @abstractmethod
+    async def drawing_template_save(
+        self, path: str, name: str | None = None, description: str | None = None
+    ) -> dict:
+        """Save the current drawing as a template.
+
+        ``.dxf`` writes on both engines; ``.dwt`` writes on the live engine
+        (``SaveAs(path, ac2018_Template)``) and raises
+        ``UnsupportedCapabilityError("dwt_write")`` headlessly. Returns
+        ``{ok, path, format: "dxf"|"dwt", backend, name, description_written}``.
+        """
+        ...