Environment variable that overrides the Forest data directory, taking
precedence over both the configuration file and the built-in default. Named
after Lotus’ LOTUS_PATH to ease switching between implementations.
Returns the effective Forest data directory: the FOREST_DATA_DIR_ENV
environment variable if set, otherwise the built-in default. Unlike
read_config, this does not consult a configuration file and is meant for
contexts (e.g. the RPC client) that need the data directory without loading
the full configuration.
Returns the path to the RPC admin token within the effective data directory
(see default_data_dir). This is where a daemon started with the same
environment saves the token, so clients can read it back from here.