Replace the Unicode prefix string approach (└─ / ├─ / │ built up as text
in a single <span class="rqe-tree-indent">) with positioned DOM elements
that draw real lines:
- rqe-tree-guide: fixed-width ancestor column, optionally draws a full
vertical border-left when the ancestor has siblings below it
(.rqe-tree-guide-line).
- rqe-tree-connector: draws the L/T shape via ::before (vertical stem,
top→center for last child, full height for mid child) and ::after
(horizontal spur, center→right). .rqe-tree-connector-last vs
.rqe-tree-connector-mid controls stem length.
renderTreeNode() now takes ancestorLines: boolean[] instead of a prefix
string. Each entry is true when the ancestor at that depth was not the
last child (so a vertical guide is still needed through that column).
childAncestorLines propagates depth === 0 correctly (root nodes have no
guide columns, so their children start with an empty array).
Lines are drawn with var(--border) so they follow the theme and work at
any font size without alignment drift. Addresses the review note on PR 2686.
ffb2d78a56