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/qr.fish

@@ -1,7 +1,20 @@
 # Copyright (C) 2026 Rootiest
 # SPDX-License-Identifier: AGPL-3.0-or-later
 
-# Generate a QR code from text or pipe
+# SYNOPSIS
+#   qr [text...]
+#
+# DESCRIPTION
+#   Generates a UTF-8 QR code from the given text or from stdin if no
+#   argument is provided. Uses qrencode locally if available, otherwise
+#   falls back to the qrenco.de API via curl.
+#
+# ARGUMENTS
+#   text...  Text to encode; reads from stdin if omitted
+#
+# EXAMPLE
+#   qr "https://example.com"
+#   echo "hello" | qr
 function qr --description 'Generate a QR code from text or pipe'
     if type -q qrencode
         if set -q argv[1]