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/_fzf_search_history.fish

@@ -0,0 +1,39 @@
+function _fzf_search_history --description "Search command history. Replace the command line with the selected command."
+    # history merge incorporates history changes from other fish sessions
+    # it errors out if called in private mode
+    if test -z "$fish_private_mode"
+        builtin history merge
+    end
+
+    if not set --query fzf_history_time_format
+        # Reference https://devhints.io/strftime to understand strftime format symbols
+        set -f fzf_history_time_format "%m-%d %H:%M:%S"
+    end
+
+    # Delinate time from command in history entries using the vertical box drawing char (U+2502).
+    # Then, to get raw command from history entries, delete everything up to it. The ? on regex is
+    # necessary to make regex non-greedy so it won't match into commands containing the char.
+    set -f time_prefix_regex '^.*? │ '
+    # Delinate commands throughout pipeline using null rather than newlines because commands can be multi-line
+    set -f commands_selected (
+        builtin history --null --show-time="$fzf_history_time_format │ " |
+        _fzf_wrapper --read0 \
+            --print0 \
+            --multi \
+            --scheme=history \
+            --prompt="History> " \
+            --query=(commandline) \
+            --preview="string replace --regex '$time_prefix_regex' '' -- {} | fish_indent --ansi" \
+            --preview-window="bottom:3:wrap" \
+            $fzf_history_opts |
+        string split0 |
+        # remove timestamps from commands selected
+        string replace --regex $time_prefix_regex ''
+    )
+
+    if test $status -eq 0
+        commandline --replace -- $commands_selected
+    end
+
+    commandline --function repaint
+end