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/cleanup.fish

@@ -1,7 +1,15 @@
 # Copyright (C) 2026 Rootiest
 # SPDX-License-Identifier: AGPL-3.0-or-later
 
-# Log orphans to ~/.removed_orphans and remove them
+# SYNOPSIS
+#   cleanup
+#
+# DESCRIPTION
+#   Identifies and removes Arch Linux orphan packages using pacman. Logs
+#   package names and versions to ~/.removed_orphans before removal.
+#
+# EXAMPLE
+#   cleanup
 function cleanup --description 'Log orphans to ~/.removed_orphans and remove them'
     set -l orphans (pacman -Qtdq)
     if test -n "$orphans"