perf(web,desktop): stop re-doing work on every render and unblock the login-shell probe#23857

fix(desktop): login shell probe no longer hangs on stderr output

fix(web): useLocalStorage reuses its JSON codec across renders

fix(web): diff panel no longer re-parses the patch on every render

fix(web): streaming markdown keeps its incremental parse cache across renders

test(web): bench terminal link extraction on dense vs spaced lines