fix(05-03): normalize shared-volume attachment paths

- strip /workspace and /agents roots before forwarding attachments upstream
- reuse the same normalization for send-file events returned to Matrix

sdk/real.py

@@ -191,6 +191,27 @@ class RealPlatformClient(PlatformClient):
         code = getattr(exc, "code", None) or "PLATFORM_CONNECTION_ERROR"
         return PlatformError(str(exc), code=code)
 
+    @staticmethod
+    def _normalize_workspace_path(location: str) -> str | None:
+        if not location:
+            return None
+
+        path = Path(location)
+        if not path.is_absolute():
+            normalized = path.as_posix()
+            return normalized or None
+
+        parts = path.parts
+        if len(parts) >= 2 and parts[1] == "workspace":
+            relative = Path(*parts[2:]).as_posix()
+            return relative or None
+        if len(parts) >= 3 and parts[1] == "agents":
+            relative = Path(*parts[3:]).as_posix()
+            return relative or None
+
+        relative = path.as_posix().lstrip("/")
+        return relative or None
+
     @staticmethod
     def _attachment_paths(attachments: list[Attachment] | None) -> list[str]:
         if not attachments:
@@ -198,18 +219,18 @@ class RealPlatformClient(PlatformClient):
         paths = []
         for attachment in attachments:
             if attachment.workspace_path:
-                paths.append(attachment.workspace_path)
+                normalized = RealPlatformClient._normalize_workspace_path(
+                    attachment.workspace_path
+                )
+                if normalized:
+                    paths.append(normalized)
         return paths
 
     @staticmethod
     def _attachment_from_send_file_event(event: MsgEventSendFile) -> Attachment:
         location = str(event.path)
         filename = Path(location).name or None
-        workspace_path = location
+        workspace_path = RealPlatformClient._normalize_workspace_path(location)
-        if workspace_path.startswith("/workspace/"):
-            workspace_path = workspace_path[len("/workspace/") :]
-        elif workspace_path == "/workspace":
-            workspace_path = ""
         return Attachment(
             url=location,
             mime_type="application/octet-stream",