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/open-url.fish

@@ -36,6 +36,9 @@
 # EXAMPLE
 #   open-url https://git.rootiest.dev/rootiest/fish-config
 #   open-url -v https://fish-config-docs.pages.dev/
+#
+# NOTES
+#   Typo abbreviation: url-open (expands to open-url on space/enter).
 function open-url --description 'Open a URL in the best available web browser'
     argparse h/help s/silent v/verbose -- $argv
     or return 1