refactor(option): simplify error buffer handling

Problem: Option validators and setters repeatedly pass error buffers and
their sizes separately. Some setters return messages in static storage.

Solution:

- Add CharBuf for borrowed writable storage, with its length including
  space for a terminating NUL.
- Move option error buffers to the callers that report errors. Preserve
  existing buffer sizes, truncation, and calls that do not need a
  message.
- Consolidate option error formatting and the duplicated code that lists
  valid option values.
- Return error messages directly from do_one_set_option().
- Remove unused arguments from get_option_newval() and
  set_option_value_for().
- Handle legacy TTY assignments in the existing callers and remove the
  redundant compatibility wrapper.
- Reuse CharBuf for Tree-sitter query errors.
- Pass CharBuf through the statusline and statuscolumn builders,
  retaining the buffer sizes provided by their callers, including title
  formatting.

AI-assisted

0 files changed, 0 insertions, 0 deletions