Editor-grade mouse selection parity with the Ink TUI (hermes-ink selection.ts):
a second click in the 500ms/1-cell chain selects the same-class character run
under the cursor (iTerm2 word set, wide-glyph aware), a third selects the line,
and dragging with the button held extends word-by-word / line-by-line while the
clicked span stays selected — anchor flips across the span on direction change.
Core knows only press-drag char selection, so this is a boundary shim
(multiClickSelect.ts) wrapping the renderer's startSelection/updateSelection
seam; word bounds read the presented frame's char grid. Native quirks probed
and pinned: per-renderable selection anchors are fixed at set time (anchor
flips restart the selection) and forward selections exclude the focus cell
(inclusive spans seed focus at hi+1). Pure scanning logic in logic/multiClick.ts;
20 new tests (pure + real-mouse-path frames); demo.tsx installs the seam for
tmux smokes.
