docs(functions): standardize all function doc blocks to UNIX man-page style

Replace all ad-hoc inline comments between license headers and function
declarations with consistent SYNOPSIS / DESCRIPTION / ARGUMENTS / RETURNS /
EXAMPLE blocks across all 99 project-owned functions/ files. No executable
logic, variable names, or exit codes were modified.

Completes Task #6 from AGENTS.md (Retroactive Function Documentation
Standardization).

functions/edit.fish

@@ -1,7 +1,18 @@
 # Copyright (C) 2026 Rootiest
 # SPDX-License-Identifier: AGPL-3.0-or-later
 
-# alias edit=nvim
+# SYNOPSIS
+#   edit [args...]
+#
+# DESCRIPTION
+#   Opens files in nvim, falling back to $EDITOR, nano, or vi if nvim is not
+#   installed.
+#
+# ARGUMENTS
+#   args...  Files and options forwarded to the editor
+#
+# EXAMPLE
+#   edit ~/.config/fish/config.fish
 function edit --wraps='nvim' --description 'alias edit=nvim'
     if type -q nvim
         nvim $argv