config(fish): add fish completions for cli tools

dot_config/fish/conf.d/30-ssh-agent.fish

@@ -0,0 +1,13 @@
+# Start or reuse a single ssh-agent shared across shells.
+# Respects an externally provided SSH_AUTH_SOCK (systemd unit, forwarding, keyring).
+if status is-interactive; and not set -q SSH_AUTH_SOCK
+    set -l env_file $HOME/.ssh/agent.env.fish
+    test -r $env_file; and source $env_file
+
+    # ssh-add exit 2 = no agent reachable (0/1 = agent alive)
+    ssh-add -l >/dev/null 2>&1
+    if test $status -eq 2
+        ssh-agent -c | string replace -r '^setenv (\S+) (\S+);$' 'set -gx $1 $2' | string match -rv '^echo ' >$env_file
+        source $env_file
+    end
+end