Problem: hidden files are dimmed via OilHidden -> Comment, and there is
no clean way to make them look identical to visible entries. Clearing
OilHidden alone causes all hidden types to lose their type-specific
coloring.
Solution: add a recipe that iterates _get_highlights() and relinks
each Oil*Hidden group to its non-hidden base. The Lua pattern
"^(Oil.+)Hidden$" naturally skips OilHidden itself and automatically
covers any future entry types.
Resolves: stevearc/oil.nvim#578
Problem: there was no example showing how to register and sort by a
custom column.
Solution: add a recipe demonstrating an "extension" column with
natural-order sorting.
Cherry-picked from: stevearc/oil.nvim#697
Problem: get_current_dir returns nil in several cases that were not
documented, causing confusion when used in keymaps that open pickers
like Telescope (#682). Also, posix_to_os_path could crash on Windows
when no drive letter is found.
Solution: expand get_current_dir docs to explain nil return cases, add
a Telescope recipe with nil guards, and add a defensive nil check in
posix_to_os_path.
Cherry-picked from: stevearc/oil.nvim#727
