Replace hardcoded truncation widths across CLI commands with
render::flex_width() calls that adapt to terminal size. Remove
server-side truncate_to_chars() in timeline collect/seed stages so
full text is preserved through the pipeline — truncation now happens
only at the presentation layer where terminal width is known.
Affected commands: explain, file-history, list (issues/mrs/notes),
me, timeline, who (active/expert/workload).
