feat: enhance README and improve environment configuration

- Added a new section in the README for Inference Providers, detailing setup instructions for Nous Portal, OpenRouter, and Custom Endpoints, improving user guidance for LLM connections.
- Updated messaging platform setup instructions to include Slack and WhatsApp, providing clearer steps for configuration.
- Introduced a new environment variable, TERMINAL_SANDBOX_DIR, to allow users to customize the sandbox storage location for Docker and Singularity environments.
- Refactored the Docker and Singularity environment classes to utilize the new sandbox directory for persistent workspaces, enhancing organization and usability.
- Improved handling of working directories across various environments, ensuring compatibility and clarity in execution paths.

tools/environments/ssh.py

@@ -24,7 +24,7 @@ class SSHEnvironment(BaseEnvironment):
     and a remote kill is attempted over the ControlMaster socket.
     """
 
-    def __init__(self, host: str, user: str, cwd: str = "/tmp",
+    def __init__(self, host: str, user: str, cwd: str = "~",
                  timeout: int = 60, port: int = 22, key_path: str = ""):
         super().__init__(cwd=cwd, timeout=timeout)
         self.host = host