feat(guards): add in-function opinionated guards and CachyOS cleanup

C1 shadows (rm, cat, ls, less, du, bash, top, ping, ssh, rg, mkdir,
help) fall back to the bare command when __fish_config_op_aliases is
falsy; rm falls back to exact 'command rm' with no wrapper. C2 gates
the auto-venv PWD hook. C3 gates smart_exit (composing with Task #4
logging), fish_right_prompt, and all six expand_bang_*/expand_typo_sub
functions atomically with the bang-bang system. C4 integration commands
(spwin, tab, split, hist, logs, upgrade) refuse with a colored stderr
error when disabled. config.fish now also strips the CachyOS distro
config's own bang-bang bindings, history override, and alias opinions
per category, restoring fish stock functions where they exist.

functions/split.fish

@@ -23,6 +23,14 @@
 #   split
 #   split -v nvim README.md
 function split --description 'Run a command in a new terminal split'
+    # Opinionated guard (C4): integrations disabled
+    if not __fish_config_op_enabled __fish_config_op_integrations
+        set -l c_err (set_color red)
+        set -l c_reset (set_color normal)
+        echo "$c_err"'split: disabled by __fish_config_op_integrations'"$c_reset" >&2
+        return 1
+    end
+
     set -l is_kitty 0
     set -l is_wezterm 0