The write/edit tools already declare card:'diff' with applied hunks on
callView/resultView, but the Web client discarded it: a mutation landed on
GenericToolCard and the details panel flattened the result to a <pre>. Add
DiffBlock (ui-primitives), diff-card-model (the single callView/resultView
derivation), and FileMutationRow (keyed under write and edit), and make the
generic fallback row and the details panel diff-aware. The +/- block form,
per-file path header, same-file gap, and footer mirror the TUI diff card;
the chat row caps at CHAT_DIFF_MAX_LINES against the panel's full height.
Chinesezjc