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/search.fish

@@ -1,6 +1,22 @@
 # Copyright (C) 2026 Rootiest
 # SPDX-License-Identifier: AGPL-3.0-or-later
 
+# SYNOPSIS
+#   search [args...]
+#
+# DESCRIPTION
+#   Delegates to paru or yay for interactive AUR package search and
+#   installation. Falls back to yay if paru is not installed.
+#
+# ARGUMENTS
+#   args...  Arguments forwarded to paru or yay
+#
+# RETURNS
+#   0  AUR helper ran successfully
+#   1  No AUR helper (paru or yay) found
+#
+# EXAMPLE
+#   search neovim
 function search --description 'Search/install packages interactively via paru or yay'
     set -l aur ""
     if type -q paru