pub fn resolve_config_dir() -> Result<PathBuf>Expand description
Resolve the Claude config directory at the boot boundary: honour
$CLAUDE_CONFIG_DIR (ignoring empty values), else fall back to
$HOME/.claude. After this point, the resolved path is threaded as a
typed PathBuf (via Workspace::new, which in turn binds each
Agent::spawn(config_dir) to its account’s path).
Per hard rule #14 - no cwd-derived fallbacks. When $CLAUDE_CONFIG_DIR
is unset/empty AND dirs::home_dir() returns None, refuse to launch
rather than substituting ./.claude.