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/gemini-resume.fish

@@ -1,7 +1,17 @@
 # Copyright (C) 2026 Rootiest
 # SPDX-License-Identifier: AGPL-3.0-or-later
 
-function gemini-resume
+# Execute gemini-resume
+function gemini-resume --description 'Execute gemini-resume'
+    if not type -q gemini-cli
+        echo "Error: The 'gemini-cli' command is not installed or not in PATH." >&2
+        return 1
+    end
+    if not type -q save_gemini_session
+        echo "Error: The companion function 'save_gemini_session' is missing." >&2
+        return 1
+    end
+
     if test -f .gemini_session
         set -l sid (cat .gemini_session)
         # Use --resume (or -r) to jump back in