{#
  Brutalist crosshair marker: slab-filled rect with a centered cross.
  Context: {x, y, size, half, cross}. Invoked via chart_markers loop.
#}
<g transform="translate({{ m.x }},{{ m.y }})">
  <rect x="{{ m.neg_half }}" y="{{ m.neg_half }}" width="{{ m.size }}" height="{{ m.size }}"
        fill="var(--dna-surface)" stroke="var(--dna-signal-dim,var(--dna-signal))" stroke-width="1"/>
  <line x1="{{ m.neg_cross }}" y1="{{ m.cross_center }}" x2="{{ m.cross }}" y2="{{ m.cross_center }}"
        stroke="var(--dna-signal-dim,var(--dna-signal))" stroke-width="1"/>
  <line x1="{{ m.cross_center }}" y1="{{ m.neg_cross }}" x2="{{ m.cross_center }}" y2="{{ m.cross }}"
        stroke="var(--dna-signal-dim,var(--dna-signal))" stroke-width="1"/>
</g>
