Fix project reopen persistence

backend/gds_builder.py

@@ -4,12 +4,11 @@
 # Developer : Qin Yue @ 2026
 # Organization : OptiHK Limited
 # -----------------------------------------------------------------------------
-import os
+import tempfile
 from dataclasses import dataclass, field
-from typing import Dict, List
-
-import yaml
+from typing import List
 
+from layout_files import load_layout_cell_files, write_layout_cells_to_directory
 from router_dependency import require_router_stack
 
 
@@ -31,16 +30,25 @@ def build_project_gds(
     prefer_full_gds: bool = False,
 ) -> BuildResult:
     """Build a hierarchical project GDS from saved cell YAML files with mxpic_router."""
-    cells = _load_project_cells(project_dir)
+    cells, warnings = _load_project_cells(project_dir)
     if not cells:
         raise ValueError("No saved cell YAML files found for this project")
 
-    return _build_with_mxpic_router(
-        project_dir,
-        output_path,
-        pdk_public_root,
-        technology_manifest_path,
-        prefer_full_gds,
+    with tempfile.TemporaryDirectory(prefix="mxpic_gds_project_") as staged_project_dir:
+        write_layout_cells_to_directory(cells, staged_project_dir)
+        result = _build_with_mxpic_router(
+            staged_project_dir,
+            output_path,
+            pdk_public_root,
+            technology_manifest_path,
+            prefer_full_gds,
+        )
+
+    return BuildResult(
+        output_path=result.output_path,
+        engine=result.engine,
+        cells_built=result.cells_built,
+        warnings=warnings + result.warnings,
     )
 
 
@@ -70,15 +78,6 @@ def _build_with_mxpic_router(
     )
 
 
-def _load_project_cells(project_dir: str) -> Dict[str, dict]:
+def _load_project_cells(project_dir: str):
     """Load saved cell YAML documents from a project directory."""
-    cells = {}
-    for filename in sorted(os.listdir(project_dir)):
-        if not filename.lower().endswith((".yml", ".yaml")):
-            continue
-        path = os.path.join(project_dir, filename)
-        with open(path, "r", encoding="utf-8") as file:
-            data = yaml.safe_load(file) or {}
-        cell_name = str(data.get("name") or os.path.splitext(filename)[0])
-        cells[cell_name] = data
-    return cells
+    return load_layout_cell_files(project_dir)