Replaces the per-row 'highlight whole row' feedback (operator
couldn't tell whether the new step would land before or after the
hovered row) with a precise insertion-point indicator.
How it works:
- Each row's onDragOver computes ev.clientY vs row midpoint.
Above midpoint → insertion index = rowIndex (BEFORE).
Below midpoint → insertion index = rowIndex + 1 (AFTER).
- An <o_fp_drop_indicator> div lives BEFORE the first row and
AFTER every row. When state.dragOverIndex matches that slot's
index, the div expands from height:0 to a 2.25rem dashed-green
reservation strip with a ghost-preview chip ('↓ insert here →
<icon> <step name>').
- onDragStart captures the dragged step/template's name + icon
into state.dragPreviewLabel/Icon for the chip text.
- Smooth 80ms height/margin transition so the line glides between
slots as the cursor moves rather than blinking.
- Trailing dropzone retains its existing 'Drop here to add at end'
styling. Empty list shows 'Drag a library step here to start'.
- onDrop reads from state.dragOverIndex (set by the most-recent
onDragOver) so we drop at the simulated position exactly.
- onDragLeave guards against child-element flicker via
relatedTarget contains() check.
- onDragEnd clears state.dragPreviewLabel/Icon so a half-completed
drag (cancelled by Esc) doesn't leave the chip stuck on screen.
fusion_plating → 19.0.10.4.0.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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