fix: clone workspace into repo-named subdirectory directly

Git clone with an explicit destination puts the working copy directly into
that directory; it does not create a repo-named subdirectory. The previous
change assumed the opposite, so workspaces ended up at
/data/working-copies/{workspace_id}/ with the repo contents mixed in,
causing a 500 when the expected repo-named subdirectory was missing.

- Build the target path as /data/working-copies/{workspace_id}/{repo_name}/
  and pass it directly to GitService.clone
- Remove stale directory detection and fallback logic that is no longer
  needed
- Keep diagnostic logging around git clone failures

Quality gates:
- pytest tests/unit: 219 passed
- mypy: clean on changed files

apps/api/src/services/shared/workspace_manager.py

@@ -104,20 +104,21 @@ class WorkspaceManager:
         repo_dir_name = self._repo_directory_name(repo)
         workspace_id = uuid.uuid4()
         parent_path = os.path.join(self.BASE_PATH, str(workspace_id))
-        clone_target = parent_path  # git clone creates {repo_dir_name}/ inside this
+        expected_path = os.path.join(parent_path, repo_dir_name)
 
         logger.info(
-            "Creating workspace: id=%s name=%s repo=%s branch=%s",
+            "Creating workspace: id=%s name=%s repo=%s branch=%s target=%s",
             workspace_id,
             name,
             repo.id,
             branch,
+            expected_path,
         )
 
         # Remove stale directory from previous failed/aborted clone
-        if os.path.exists(parent_path):
-            logger.warning("Removing stale workspace directory: %s", parent_path)
-            shutil.rmtree(parent_path, ignore_errors=True)
+        if os.path.exists(expected_path):
+            logger.warning("Removing stale workspace directory: %s", expected_path)
+            shutil.rmtree(expected_path, ignore_errors=True)
 
         os.makedirs(parent_path, exist_ok=True)
         # Ensure container users (various UIDs) can write to workspace dirs
@@ -141,7 +142,7 @@ class WorkspaceManager:
 
         try:
             await GitService.clone(
-                repo.remote_url, branch, clone_target, ssh_key=ssh_key
+                repo.remote_url, branch, expected_path, ssh_key=ssh_key
             )
         except Exception as exc:
             logger.error(
@@ -153,29 +154,6 @@ class WorkspaceManager:
             )
             raise
 
-        expected_path = os.path.join(parent_path, repo_dir_name)
-        if not os.path.isdir(expected_path):
-            # git clone can create a different directory name than expected for
-            # some URL shapes; fall back to the single directory git created.
-            entries = [
-                entry
-                for entry in os.listdir(parent_path)
-                if os.path.isdir(os.path.join(parent_path, entry))
-            ]
-            logger.info(
-                "Workspace %s: expected %s/ but found directories: %s",
-                workspace_id,
-                repo_dir_name,
-                entries,
-            )
-            if len(entries) == 1:
-                expected_path = os.path.join(parent_path, entries[0])
-            else:
-                raise RuntimeError(
-                    f"Expected git clone to create {repo_dir_name}/ under "
-                    f"{parent_path}, but found: {entries}"
-                )
-
         self._make_world_writable(expected_path)
 
         workspace = Workspace(