fix(docker): gate cwd workspace mount behind config

Keep Docker sandboxes isolated by default. Add an explicit terminal.docker_mount_cwd_to_workspace opt-in, thread it through terminal/file environment creation, and document the security tradeoff and config.yaml workflow clearly.

hermes_cli/config.py

@@ -118,6 +118,9 @@ DEFAULT_CONFIG = {
         # Each entry is "host_path:container_path" (standard Docker -v syntax).
         # Example: ["/home/user/projects:/workspace/projects", "/data:/data"]
         "docker_volumes": [],
+        # Explicit opt-in: mount the host cwd into /workspace for Docker sessions.
+        # Default off because passing host directories into a sandbox weakens isolation.
+        "docker_mount_cwd_to_workspace": False,
         # Persistent shell — keep a long-lived bash shell across execute() calls
         # so cwd/env vars/shell variables survive between commands.
         # Enabled by default for non-local backends (SSH); local is always opt-in
@@ -1407,6 +1410,7 @@ def set_config_value(key: str, value: str):
         "terminal.singularity_image": "TERMINAL_SINGULARITY_IMAGE",
         "terminal.modal_image": "TERMINAL_MODAL_IMAGE",
         "terminal.daytona_image": "TERMINAL_DAYTONA_IMAGE",
+        "terminal.docker_mount_cwd_to_workspace": "TERMINAL_DOCKER_MOUNT_CWD_TO_WORKSPACE",
         "terminal.cwd": "TERMINAL_CWD",
         "terminal.timeout": "TERMINAL_TIMEOUT",
         "terminal.sandbox_dir": "TERMINAL_SANDBOX_DIR",