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/lt.fish

@@ -1,7 +1,18 @@
 # Copyright (C) 2026 Rootiest
 # SPDX-License-Identifier: AGPL-3.0-or-later
 
-# Tree listing, depth 2
+# SYNOPSIS
+#   lt [args...]
+#
+# DESCRIPTION
+#   Displays a directory tree limited to depth 2 with icons. Uses eza,
+#   falls back to lsd, then to system ls -R.
+#
+# ARGUMENTS
+#   args...  Arguments forwarded to the listing command
+#
+# EXAMPLE
+#   lt ~/projects
 function lt --description 'Tree listing, depth 2'
     if which eza >/dev/null 2>&1
         eza --tree --level=2 --icons --color=auto --hyperlink $argv