refactor(shell): modularize shell config into per-shell profiles and conf.d

Split bash config into dedicated aliases and profile files. Extract
fish shell init from config.fish into composable conf.d fragments
(setup, environment, ssh-auth-sock). Remove the generic profile in
favor of the bash-specific one. Add a static SSH_AUTH_SOCK symlink
so tmux sessions always see the current socket regardless of which
shell spawned them.

config/tmux/tmux.conf

@@ -18,6 +18,10 @@ set -as terminal-feature ",foot*:RGB"
 # allow terminal scrolling
 #set -g terminal-overrides 'xterm*:smcup@:rmcup@'
 
+# Force tmux to use the static symlink path globally
+setenv -g SSH_AUTH_SOCK "$HOME/.ssh/ssh_auth_sock"
+set -g update-environment "DISPLAY XAUTHORITY"
+
 # default shell
 set -g default-shell "/usr/bin/fish"