service.py: use ifcopenshell.file.from_string() instead of temp file

ifcopenshell can parse IFC bytes in-memory via from_string(); no need to
write a temp file, read it back, and unlink it. Simpler and faster.
Update README library example to match.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

README.md

@@ -88,7 +88,6 @@ ifcurl render "ifc://..." -o output.png
 Use as a library:
 
 ```python
-import os, tempfile
 import ifcopenshell
 from ifcurl import IfcUrl, fetch_ifc
 from ifcurl.render import render
@@ -98,15 +97,7 @@ url = IfcUrl.parse(
     "?path=models/building.ifc&selector=IfcWall&visibility=ghost"
 )
 hexsha, ifc_bytes = fetch_ifc(url)   # hexsha is stable even for mutable refs
-
-# ifcopenshell.open() requires a file path, not bytes
-tmp_fd, tmp_path = tempfile.mkstemp(suffix=".ifc")
-try:
-    os.write(tmp_fd, ifc_bytes)
-    os.close(tmp_fd)
-    model = ifcopenshell.open(tmp_path)
-finally:
-    os.unlink(tmp_path)
+model = ifcopenshell.file.from_string(ifc_bytes.decode())
 
 png = render(model, selector=url.selector, clips=url.clips or None,
              camera=url.camera, fov=url.fov, visibility=url.visibility)

ifcurl/service.py

@@ -38,7 +38,6 @@ from __future__ import annotations
 import hashlib
 import ipaddress
 import os
-import tempfile
 import threading
 import time
 
@@ -225,18 +224,10 @@ def _t4m_put(url: str, png: bytes) -> None:
 # ---------------------------------------------------------------------------
 
 def _load_model(ifc_bytes: bytes) -> ifcopenshell.file:
-    tmp_fd, tmp_path = tempfile.mkstemp(suffix=".ifc")
     try:
-        os.write(tmp_fd, ifc_bytes)
-        os.close(tmp_fd)
-        return ifcopenshell.open(tmp_path)
+        return ifcopenshell.file.from_string(ifc_bytes.decode())
     except Exception as exc:
         raise HTTPException(status_code=422, detail=f"Could not parse IFC file: {exc}") from exc
-    finally:
-        try:
-            os.unlink(tmp_path)
-        except OSError:
-            pass
 
 
 # ---------------------------------------------------------------------------