* fix(plugin): allow command chaining with bar separator
Problem: :Pending|only failed because the command definition lacked the
bar attribute, causing | to be consumed as an argument.
Solution: Add bar = true to nvim_create_user_command so | is treated as
a command separator, matching fugitive's :Git behavior.
* refactor(buffer): remove opinionated window options
Problem: The plugin hardcoded number, relativenumber, wrap, spell,
signcolumn, foldcolumn, and cursorline in set_win_options, overriding
user preferences with no way to opt out.
Solution: Remove all cosmetic window options. Users who want them can
set them in after/ftplugin/pending.lua. Only conceallevel,
concealcursor, and winfixheight remain as functionally required.
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