fix: remove broken ~ expansion, require working_directory for relative paths

apps/api/src/api/tool_instances.py

@@ -110,17 +110,16 @@ async def _resolve_single_git_mount(
         logger.warning("Invalid git mount skipped: missing remote_url or target_path")
         return []
     
-    # Expand ~ to the working directory or a default home path
-    # (The container may have HOME set to /tmp, so we resolve it ourselves)
-    if target_path.startswith("~"):
-        home = working_directory or "/home/user"
-        target_path = home + target_path[1:]
-        logger.info("Expanded ~ to %s", target_path)
-    
     # Resolve relative target paths against working directory
     if target_path and not target_path.startswith("/"):
-        base = working_directory or "/home/user"
-        target_path = os.path.join(base, target_path)
+        if not working_directory:
+            logger.warning(
+                "Git mount skipped: target_path '%s' is relative but no working_directory is configured. "
+                "Set working_directory in the tool config or use an absolute path.",
+                target_path
+            )
+            return []
+        target_path = os.path.join(working_directory, target_path)
         logger.info("Resolved relative target path to %s", target_path)
     
     if not instance_dir: