Text object follow-ups: count, visual-mode escape, empty pairs

[oribarilan]

Known limitations left over from the text-object work (#68, #69). Three small, independent items, tracked together.

• Count on objects. d2iw acts as diw because the count is ignored on text objects. Apply it in the textobject dispatch in src/vim/normal.ts.
• vi<Esc> stays in visual. With a pending text object, Esc cancels the object but stays in visual mode, so leaving takes a second Esc. The dispatch in src/vim/visual.ts runs before the escape handler, so a fall-through fix also has to clear the pending state, or it leaks into normal mode.
• Empty-pair inner no-ops. di" on "" and ci( on () do nothing. Supporting ci( on an empty pair needs a zero-width-insert convention that the deleteRange action model can't express yet.