feat: initial fish shell configuration

- Core config layered on CachyOS base with Catppuccin Mocha theming
- Fisher plugins: fzf.fish, catppuccin, autopair, replay, puffer-fish, magic-enter, spark
- Smart CLI wrappers with fallbacks (bat, lsd, btop, dust, prettyping)
- Custom functions: git, docker, network, kitty, AI session management
- Extensive abbreviation system for keyboard-driven workflows
- Secrets/local sourcing pattern for private and machine-specific config
- README with full documentation and personalization guide
- AGPLv3+ license with copyright headers on all source files

functions/du.fish

@@ -0,0 +1,63 @@
+# Copyright (C) 2026 Rootiest
+# SPDX-License-Identifier: AGPL-3.0-or-later
+
+function du
+    set cmd ""
+    set args
+
+    # Parse override flags and gather remaining args
+    for arg in $argv
+        switch $arg
+            case --disk
+                set cmd duf
+            case --dir
+                set cmd dust
+            case --dua
+                set cmd dua
+            case '*'
+                set args $args $arg
+        end
+    end
+
+    # Autodetect if no override flag given
+    if test -z "$cmd"
+        if count $args
+            set first_arg $args[1]
+            if test -d "$first_arg" -o -f "$first_arg"
+                set cmd dust
+            else
+                set cmd duf
+            end
+        else
+            set cmd duf
+        end
+    end
+
+    # Tool execution with graceful fallback
+    switch $cmd
+        case duf
+            if type -q duf
+                duf $args
+            else
+                echo "(duf not found — falling back to du)"
+                command du -sh $args
+            end
+        case dust
+            if type -q dust
+                dust $args
+            else
+                echo "(dust not found — falling back to du)"
+                command du -sh $args
+            end
+        case dua
+            if type -q dua
+                dua $args
+            else
+                echo "(dua not found — falling back to du)"
+                command du -sh $args
+            end
+        case '*'
+            # This shouldn't happen, but just in case
+            command du -sh $args
+    end
+end