Standard for diff and read output: the line number (and the +/- marker for
diffs) is the coloured anchor; the content itself reads plainly.

diff: "{num} {marker}  {content}" with num+marker in the marker colour
(green/red), content neutral. Fixed the number-column regex to "^( +)(\d+)|"
so files with more than 9 lines (width > 1) still match — the old
single-space pattern silently fell back to whole-line colouring.
read: "{num}: {content}" with the number in the accent colour, content
neutral (was dim number).

Applied to both clients: the TUI diff/filesystem renderers and the webclient
ToolCard (renderDiff / renderRead). The model-facing text from the server is
unchanged — this is display-only.