feat(experimental): Web band for Claude Code mods

A Client package mounts the bridge's Remote contribution, watches each
session's band through watchBand, draws the serialized tree in the input
dock with Claude Code's Box/Text/Button vocabulary on this theme's tokens,
and sends button clicks back through pressBand with the generation they
were drawn in. An opt-in overlay composes the bridge, the band, and the
three example mods for a source launch.