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/fast-cli.fish

@@ -1,7 +1,17 @@
 # Copyright (C) 2026 Rootiest
 # SPDX-License-Identifier: AGPL-3.0-or-later
 
-# Run a speed test using fast.com
+# SYNOPSIS
+#   fast-cli [args...]
+#
+# DESCRIPTION
+#   Runs a network speed test using the fast.com CLI tool.
+#
+# ARGUMENTS
+#   args...  Arguments forwarded to the fast command
+#
+# EXAMPLE
+#   fast-cli
 function fast-cli --description "Run a speed test using fast.com"
     command fast $argv
 end