Bump logprob sparkline target to 1000 points

Power-of-two subsampling for logprob sparkline (fewer step transitions)

Add per-token logprob sparkline under the legend, gradient-stroked to match colormap

Long-sequence rendering: coarse spans, incremental append, rAF throttle, lpRange-threshold full repaint

Dynamic bases-per-line based on output width

Move copy button inside seq-block (top-right)

Add copy button, dynamic logprob range, base/logprob bg tints, examples-above-input layout

Initial demo: streaming DNA continuation with logprob coloring