feat(shell): add CachyOS-derived tricks.fish and copy utilities

Adds conf.d/tricks.fish (PATH additions for ~/.local/bin and depot_tools,
bang-bang key bindings, history timestamp override, backup utility) and
functions/copy.fish (smarter cp wrapper that strips trailing slashes from
source directories, fixing a CachyOS-specific cp quirk).

Updates config.fish to explicitly source copy.fish on startup and refactors
several conditional blocks to single-line style for consistency. Syncs
README.md to document all new utilities.

conf.d/tricks.fish

@@ -0,0 +1,67 @@
+# Copyright (C) 2026 Rootiest
+# SPDX-License-Identifier: AGPL-3.0-or-later
+
+#           ────── Borrowed and modified from CachyOS config ─────────
+#          ╭──────────────────────────────────────────────────────────╮
+#          │       Provides PATH additions, bang-bang helpers,        │
+#          │               and history/backup utilities               │
+#          ╰──────────────────────────────────────────────────────────╯
+## Environment setup
+# Apply .profile: use this to put fish compatible .profile stuff in
+if test -f ~/.fish_profile
+    source ~/.fish_profile
+end
+
+# Add ~/.local/bin to PATH
+if test -d ~/.local/bin
+    if not contains -- ~/.local/bin $PATH
+        set -p PATH ~/.local/bin
+    end
+end
+
+# Add depot_tools to PATH
+if test -d ~/Applications/depot_tools
+    if not contains -- ~/Applications/depot_tools $PATH
+        set -p PATH ~/Applications/depot_tools
+    end
+end
+
+## Functions
+# Functions needed for !! and !$ https://github.com/oh-my-fish/plugin-bang-bang
+function __history_previous_command
+    switch (commandline -t)
+        case "!"
+            commandline -t $history[1]
+            commandline -f repaint
+        case "*"
+            commandline -i !
+    end
+end
+
+function __history_previous_command_arguments
+    switch (commandline -t)
+        case "!"
+            commandline -t ""
+            commandline -f history-token-search-backward
+        case "*"
+            commandline -i '$'
+    end
+end
+
+if [ "$fish_key_bindings" = fish_vi_key_bindings ]
+
+    bind -Minsert ! __history_previous_command
+    bind -Minsert '$' __history_previous_command_arguments
+else
+    bind ! __history_previous_command
+    bind '$' __history_previous_command_arguments
+end
+
+# Fish command history
+function history
+    builtin history --show-time='%F %T '
+end
+
+function backup --argument filename
+    cp $filename $filename.bak
+end