Per-edge border props (borderTop/Bottom/Left/Right) reserved 1 yoga cell
whenever truthy, regardless of borderStyle. Since these props default to
`true`, toggling one on an UPDATE while borderStyle stays unset (Vue patches
only the changed per-edge prop, not borderStyle) left a spurious 1-cell inset
with no border ever drawn — content shifted to "\n HELLO" instead of "HELLO".
Mirror Ink's applyBorderStyles: an edge's width is `borderStyle ? 1 : 0`,
forced to 0 when that edge is explicitly `false`. A per-edge toggle can only
SUBTRACT, never add. The per-edge yoga setters become no-ops; patchProp now
recomputes all four edges from el.props on any border-prop change via the new
reconcileBorderEdges helper, so borderStyle flipping in EITHER direction
(set->unset zeroes, unset->set re-reserves) and per-edge toggles are all
handled jointly — the computation a single (n, v) yoga setter cannot do.
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Yunfei He
a2d33d98fe