remove path traversal restriction from file tools

Container isolation is sufficient — agents can access the full
filesystem. Absolute paths are passed through as-is.

server/main.py

@@ -483,11 +483,8 @@ def _get_pty(session_id: str) -> PtySession:
 
 
 def _workspace_path(rel: str) -> pathlib.Path:
-    """Resolve a relative path inside WORKSPACE, reject path traversal."""
-    p = (pathlib.Path(WORKSPACE) / rel).resolve()
-    if not str(p).startswith(str(pathlib.Path(WORKSPACE).resolve())):
-        raise ValueError(f"Path escapes workspace: {rel}")
-    return p
+    p = pathlib.Path(rel)
+    return p if p.is_absolute() else pathlib.Path(WORKSPACE) / rel
 
 
 def _get_job(job_id: str) -> BackgroundJob: