- rainbow-dark.theme: revert line_start back to the stock '-!-' pattern.
- .irssi/scripts/autorun/rainbow-timestamp.pl: new autorun script that
hooks 'print text', matches a leading HH:MM[:SS], and reruns it
through rainbow.pl's make_colors (same palette [4,8,9,11,12,13],
same 2-char stride, same phase-advance on each line). The result
is that every successive timestamp is a 5-character rainbow
gradient that also shifts starting colour line-to-line.