2a5aef2a64
Allow users to customize the location of their private overlay directory via `set -U __fish_user_dots_path /your/path`. Falls back to the previous hardcoded default of `$XDG_CONFIG_HOME/.user-dots/fish` when unset. Simplify the sourcing model: config.fish now sources only local.fish, which is responsible for sourcing its own secrets.fish companion. The redundant direct sourcing of secrets.fish from config.fish is removed. Update docs/fish-config.md (Sections 1, 7, 10) and README.md to document the new variable, the custom-path override pattern, and the simplified sourcing model.