docs(functions): merge manual-only examples and notes into headers

Folds the examples Section 5 carried but the headers did not into each
function's `# EXAMPLE`, and moves the three lines that only looked like
examples -- the two typo-abbreviation notes and rm's /usr/bin/rm fallback --
into `# NOTES`, the label already in use.

Also corrects gi's synopsis, which omitted -l, and documents yt-dlp's
--no-embed-thumbnail in `# ARGUMENTS`.

functions/rm.fish

@@ -33,6 +33,9 @@
 #   rm file.txt
 #   rm -e
 #   rm -S sensitive_key.pem
+#
+# NOTES
+#   Falls back to /usr/bin/rm when trash is unavailable.
 function rm --description 'Ultimate rm: trash, list, empty, and secure-erase'
     # Opinionated guard (C1): fall back to bare command rm when disabled.
     if not __fish_config_op_enabled __fish_config_op_aliases