feat: add Fish function wrappers for copilot suggest/explain commands

Replace gh copilot aliases with custom Fish functions that provide better help
text and wrap the copilot CLI with appropriate prompts

home/dot_config/fish/functions/explain.fish

@@ -0,0 +1,28 @@
+function explain --description "Explain a command using GitHub Copilot"
+    argparse --name=explain \
+        'd/debug' \
+        'h/help' \
+        'hostname=' \
+        -- $argv
+    or return 1
+
+    if set -q _flag_help
+        echo "Wrapper around \`copilot\` to explain a command."
+        echo
+        echo "USAGE"
+        echo "  explain [flags] <command>"
+        echo
+        echo "FLAGS"
+        echo "  -d, --debug            Enable debugging"
+        echo "  -h, --help             Display help usage"
+        echo "      --hostname HOST    GitHub host for authentication"
+        echo
+        echo "EXAMPLES"
+        echo "  explain 'du -sh | sort -h'"
+        echo "  explain 'git log --oneline --graph --decorate --all'"
+        echo "  explain 'bfg --strip-blobs-bigger-than 50M'"
+        return 0
+    end
+
+    copilot -p "explain: $argv" --allow-all-tools
+end