refactor(functions): standardize documentation, metadata, and wrappers

- Add comprehensive `--description` flags to all fish functions for better `help` and `functions` output.
- Introduce and correct `--wraps` flags to ensure proper completions for aliased commands (e.g., `top` wrapping `btop`, `zellij`, `upgrade` wrapping `paru`).
- Prepend descriptive comments before function definitions for better source readability.
- Add standard copyright and SPDX license identifiers to shell scripts.
- Enhance script robustness by ensuring consistent terminal checks (Kitty, WezTerm) and graceful fallbacks in window/tab spawning functions (`spwin`, `tab`).
- Implement graceful fallbacks to basic core utilities when preferred modern alternatives are missing (e.g., `top` falling back to system `top` if `btop` is missing, `view` falling back to `less` or `cat` if `nvim` is unavailable).
- Improve overall code consistency across the `functions/` directory.

functions/gip6.fish

@@ -1,7 +1,8 @@
 # Copyright (C) 2026 Rootiest
 # SPDX-License-Identifier: AGPL-3.0-or-later
 
-function gip6 -d "Get public IPv6 address"
+# Get public IPv6 address
+function gip6 --description 'Get public IPv6 address'
     # Use -6 to force IPv6 and --fail to catch network errors
     set -l ip (curl -6 -s --fail https://icanhazip.com 2>/dev/null)